I am new in Android Studio so I face some problem with it. I am looking for a way how to project clean.
In Eclipse I would do Project -> Clean -> OK
but I don't know how it is done with Android Studio.
You can clean your project doing this
Build > Clean Project
or Build > Rebuild Project
Also you can do the gradlew clean
As @Kellogs commented :
Manually delete the [project]/.gradle
as hidden folder
as that one is the main culprit for large cleaned projects sizes.