A two-stroke engine comprising: a scavenging passage opening in a combustion chamber in a scavenging stroke to fill the combustion chamber with a working gas containing a combustion fuel; a scavenge filling chamber communicating through a communicating port with the scavenging passage and arranged to be filled with a non-working gas in a fuel weight concentration smaller than that of the working gas prior to the scavenging stroke; and a cylinder block forming the combustion chamber, a piston to reciprocate in the combustion chamber, and a crank chamber into which the working gas is to be introduced through an intake port. wherein in the scavenging stroke the scavenging passage and the scavenge filling chamber are made open in the combustion chamber and the non-working gas in the scavenge filling chamber is forced into the combustion chamber by the working gas inside the scavenging passage through the communicating port to scavenge the combustion chamber, characterized in that the scavenging passage and the scavenge filling chamber extend in the cylinder block so as to be adjacent to each other along an axial direction of the combustion chamber. the scavenge fitting chamber has an aperture to open in the combustion chamber when the piston is located at a position near a bottom dead center, the scavenging passage has an aperture to open in the combustion chamber when the piston is located at a position near the bottom dead center, and one end of the scavenging passage is in communication with the crank chamber, and the communicating port opens in a bulkhead interposed between the scavenging passage and the scavenge filling chamber and an opening direction thereof is perpendicular to a gas flow direction in the scavenging passage. a scavenging passage opening in a combustion chamber in a scavenging stroke to fill the combustion chamber with a working gas containing a combustion fuel; a scavenge filling chamber communicating through a communicating port with the scavenging passage and arranged to be filled with a non-working gas in a fuel weight concentration smaller than that of the working gas prior to the scavenging stroke; and a cylinder block forming the combustion chamber, a piston to reciprocate in the combustion chamber, and a crank chamber into which the working gas is to be introduced through an intake port. wherein in the scavenging stroke the scavenging passage and the scavenge filling chamber are made open in the combustion chamber and the non-working gas in the scavenge filling chamber is forced into the combustion chamber by the working gas inside the scavenging passage through the communicating port to scavenge the combustion chamber, characterized in that the scavenging passage and the scavenge filling chamber extend in the cylinder block so as to be adjacent to each other along an axial direction of the combustion chamber. the scavenge fitting chamber has an aperture to open in the combustion chamber when the piston is located at a position near a bottom dead center, the scavenging passage has an aperture to open in the combustion chamber when the piston is located at a position near the bottom dead center, and one end of the scavenging passage is in communication with the crank chamber, and the communicating port opens in a bulkhead interposed between the scavenging passage and the scavenge filling chamber and an opening direction thereof is perpendicular to a gas flow direction in the scavenging passage.