Disclosed herein is an oil separator for air conditioners that is capable of separating oil from refrigerant. The oil separator comprises a shell having a cylindrical space defined therein, a refrigerant introduction pipe for introducing refrigerant into the shell, a refrigerant discharge pipe for discharging the refrigerant out of the shell, and oil-drop growth accelerating member for accelerating growth of oil drops contained in the refrigerant flowing in the shell.