An amount of air taken into an air leading type two-stroke engine is increased to enhance an engine output, and gas emission characteristic deterioration caused by blow-back is inhibited. An inhibition member 16 is disposed between a choke valve 4 in a full open position and a throttle valve 6 in a full open position. The inhibition member 16 includes, for example, a mesh member like a metal mesh. Mixed fuel containing oil is supplied to the air-fuel mixture channel 14. Numerous pores of the inhibition member 16 (mesh member) are occluded by a membrane of oil components of the mixed fuel. Consequently, entry of a blow-back flow of an air-fuel mixture from the air-fuel mixture channel 14 into the air channel 12 through the numerous pores of the flow inhibition member 16 (mesh member) can be inhibited.