Abstract: A method of bevelling the peripheral edges of port openings on the inner wall of cylinders for two-cycle engines. At least the upper and lower edges of the port opening on the inner wall of a cylinder are shaped, in advance when casting the cylinder, into concavities arcuately recessed in both axial and radial directions of the cylinder. The boundary edges between the recessed concavities and the inner wall of the cylinder are lightly bevelled by pressing or grinding so that an excellent workability, mass-productivity, and great precision can be attained.