diff --git a/src/projection/map_list.rs b/src/projection/map_list.rs
new file mode 100644
index 0000000..61eb380
--- /dev/null
+++ b/src/projection/map_list.rs
@@ -0,0 +1,153 @@
+use {
+    crate::{
+        view::{
+            Observer, ObserverBroadcast, ObserverExt, OuterViewPort, View, ViewPort,
+            list::{ListView, ListDiff}
+        },
+    },
+    std::sync::Arc,
+    std::sync::RwLock,
+};
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+impl<Item: Clone + Send + Sync + 'static> OuterViewPort<dyn ListView<Item>> {
+    pub fn map<DstItem: Clone + Send + Sync + 'static, F: Fn(&Item) -> DstItem + Send + Sync + 'static>(
+        &self,
+        f: F,
+    ) -> OuterViewPort<dyn ListView<DstItem>> {
+        let port = ViewPort::new();
+        port.add_update_hook(Arc::new(self.0.clone()));
+
+        let map = Arc::new(RwLock::new(MapListItem {
+            _phantom: std::marker::PhantomData::default(),
+            src_view: None,
+            f,
+            cast: port.inner().get_broadcast(),
+        }));
+
+        self.add_observer(map.clone());
+        port.inner().set_view(Some(map));
+        port.into_outer()
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+pub struct MapListItem<SrcItem, DstItem, SrcView, F>
+where
+    SrcItem: Clone + Send + Sync + 'static,
+    DstItem: Clone + Send + Sync + 'static,
+    SrcView: ListView<SrcItem> + ?Sized,
+    F: Fn(&SrcItem) -> DstItem + Send + Sync,
+{
+    _phantom: std::marker::PhantomData< SrcItem >,
+    src_view: Option<Arc<SrcView>>,
+    f: F,
+    cast: Arc<RwLock<ObserverBroadcast<dyn ListView<DstItem>>>>,
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+impl<SrcItem, DstItem, SrcView, F> View for MapListItem<SrcItem, DstItem, SrcView, F>
+where
+    SrcItem: Clone + Send + Sync + 'static,
+    DstItem: Clone + Send + Sync + 'static,
+    SrcView: ListView<SrcItem> + ?Sized,
+    F: Fn(&SrcItem) -> DstItem + Send + Sync,
+{
+    type Msg = ListDiff<DstItem>;
+}
+
+impl<SrcItem, DstItem, SrcView, F> ListView<DstItem> for MapListItem<SrcItem, DstItem, SrcView, F>
+where
+    SrcItem: Clone + Send + Sync + 'static,
+    DstItem: Clone + Send + Sync + 'static,
+    SrcView: ListView<SrcItem> + ?Sized,
+    F: Fn(&SrcItem) -> DstItem + Send + Sync,
+{
+    fn len(&self) -> Option<usize> {
+        self.src_view.len()
+    }
+
+    fn get(&self, idx: &usize) -> Option<DstItem> {
+        self.src_view.get(idx).as_ref().map(|item| (self.f)(item))
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+impl<SrcItem, DstItem, SrcView, F> Observer<SrcView> for MapListItem<SrcItem, DstItem, SrcView, F>
+where
+    SrcItem: Clone + Send + Sync + 'static,
+    DstItem: Clone + Send + Sync + 'static,
+    SrcView: ListView<SrcItem> + ?Sized,
+    F: Fn(&SrcItem) -> DstItem + Send + Sync,
+{
+    fn reset(&mut self, view: Option<Arc<SrcView>>) {
+        let old_len = self.len();
+        self.src_view = view;
+        let new_len = self.len();
+        /* ????
+        if let Some(len) = old_len {
+            self.cast.notify_each(0..len);
+        }
+        if let Some(len) = new_len {
+            self.cast.notify_each(0..len);
+        }
+        */
+    }
+
+    fn notify(&mut self, msg: &ListDiff<SrcItem>) {
+        let forwarded_msg =
+            match msg {
+                ListDiff::Clear => ListDiff::Clear,
+                ListDiff::Remove(idx) => ListDiff::Remove(*idx),
+                ListDiff::Insert{ idx, val } =>
+                    ListDiff::Insert {
+                        idx: *idx,
+                        val: (self.f)(val)
+                    },
+                ListDiff::Update{ idx, val } =>
+                    ListDiff::Update{
+                        idx: *idx,
+                        val: (self.f)(val)
+                    }
+            };
+        self.cast.notify(&forwarded_msg);
+    }
+}
+
+//<<<<>>>><<>><><<>><<<*>>><<>><><<>><<<<>>>>
+
+#[cfg(test)]
+mod tests {
+    use crate::buffer::vec::*;
+    use crate::projection::map_sequence::*;
+    use crate::view::{port::UpdateTask, list::ListView};
+    
+    #[test]
+    fn map_list1() {
+        let mut buffer = VecBuffer::new();
+
+        let target_port = buffer.get_port()
+            .to_list()
+            .map(|x| x + 10);
+
+        let target_view = target_port.get_view();
+
+        buffer.push(0);
+        buffer.push(7);
+        buffer.push(9);
+
+        target_port.0.update();
+
+        assert_eq!(target_view.len(), Some(3));
+
+        assert_eq!(target_view.get(&0), Some(10));
+        assert_eq!(target_view.get(&1), Some(17));
+        assert_eq!(target_view.get(&2), Some(19));
+        assert_eq!(target_view.get(&3), None);
+    }
+}
+
diff --git a/src/projection/mod.rs b/src/projection/mod.rs
index 201e305..ec95927 100644
--- a/src/projection/mod.rs
+++ b/src/projection/mod.rs
@@ -17,6 +17,7 @@ pub mod flatten_sequence;
 pub mod flatten_grid;
 pub mod map_singleton;
 pub mod map_sequence;
+pub mod map_list;
 pub mod map_index_item;
 pub mod map_index_key;
 pub mod grid_offset;