The invention relates to a cylindrical internal surface processing method. A thermally sprayed coating is deposited onto a cylindrical internal surface of a base member after a rough surface has been formed on the cylindrical internal surface. The tapered surface is configured such that the internal diameter of the axial end portion is larger than the internal diameter of the remaining portions of the cylinder bore internal surface. After the tapered surface is formed, the thermally sprayed coating is honed. This method prevents exfoliation of a thermally sprayed coating at an end portion of a cylindrical internal surface in a situation where honing or another mechanical finishing process is applied to the thermally sprayed coating after the coating is formed on the cylindrical internal surface.