A two-cycle internal combustion engine includes a control valve disposed within a communicating passage between the combustion chamber and a chamber portion adjacent to the combustion chamber. The control valve is for controlling the opening and closing of the communicating passage. Blowby of an air-fuel mixture supplied to the combustion chamber can be prevented to reduce fuel consumption and increase the exhaust gas purifying performance. A communicating passage portion between the control valve and the fuel supply opening is configured to spray fuel from the control valve to a part or all of a wall surface of the communicating passage portion and the wall surface of the communicating passage portion is shaped to guide the fuel into the combustion chamber.