To provide a two-stroke engine which achieves good fuel consumption and produces clean exhaust gas.SOLUTION: A two-stroke engine 10 includes: a piston 110 in which a combustion piston 111 which is housed in a combustion piston cylinder 210 and forms a combustion chamber with the combustion piston cylinder 210, a scavenging-air piston 112 which is housed in a scavenging-air cylinder 410 and suctions scavenging-air into the scavenging-air piston cylinder 410, and a connecting rod 113 which connects the combustion piston 111 with the scavenging-air piston 112 in an axial direction are formed in an integral structure; a scavenging-air passage 115 which penetrates through the piston 110 in the axial direction and sends air from the scavenging-air piston 112 into the combustion piston 111 through the connecting rod 113; a discharge valve 230 which opens or closes the scavenging-air passage 115; and an exhaust gas outlet 212 formed at a cylinder head of the combustion piston cylinder 210. The structure achieves good fuel consumption and makes exhaust gas clean.SELECTED DRAWING: Figure 1