diff --git a/CHANGELOG.md b/CHANGELOG.md
index 10a57fa..2a50f32 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,22 @@
+# Release 0.40.0-dev
+
+### New features since last release
+
+### Improvements 🛠
+
+### Breaking changes 💔
+
+### Deprecations 👋
+
+### Documentation 📝
+
+### Bug fixes 🐛
+
+### Contributors ✍️
+
+This release contains contributions from (in alphabetical order):
+
+---
 # Release 0.39.0
 
 ### Bug fixes 🐛
diff --git a/pennylane_qulacs/_version.py b/pennylane_qulacs/_version.py
index 9d94342..6686b8b 100644
--- a/pennylane_qulacs/_version.py
+++ b/pennylane_qulacs/_version.py
@@ -16,4 +16,4 @@
    Version number (major.minor.patch[-label])
 """
 
-__version__ = "0.39.0"
+__version__ = "0.40.0-dev"