Provided is a two stroke engine that can vary the timing of opening and closing the scavenging port (43) by using a highly simple structure. An end of the scavenging port (43) on the side of the combustion chamber (44) is defined by scavenging orifices (42c) formed in a cylinder sleeve (42), and a shutter (73, 74) is provided on the cylinder sleeve so as to selectively project into the scavenging orifices (42c) from an upper edge (42d) thereof by moving along an axial line (3X) of the cylinder bore (3a).