A chainsaw includes: an engine unit; a fuel supplying device configured to supply fuel to the engine unit; and an engine chamber defining portion defining an engine chamber therein. The engine unit includes: a cylinder unit housing a piston therein; a crankshaft configured to be driven by the piston; and a crank case configured to support the cylinder unit and house the crankshaft therein. The cylinder unit is accommodated in the engine chamber. The engine chamber defining portion has a partitioning portion interposed between the cylinder unit and the fuel supplying device and is formed with a first engine chamber venthole and a second engine chamber venthole adjacent to the cylinder unit for achieving ventilation between the engine chamber and atmosphere.