A roller lifter includes a lifter body having a cylindrical peripheral wall and a roller rotatably mounted on the lifter body via a shaft member and brought into contact with a cam. The peripheral wall has an outer periphery formed with a sliding surface which is slid on an inner wall of a cylinder. The lifter body has a rotation stopper formed by outwardly protruding a part of the peripheral wall, and an opening formed in another part of the peripheral wall which another part is radially opposed to the rotation stopper. The opening is open so that the rotation stopper oppositely faces the opening.