To keep a low friction property at a piston ring of a reciprocation mechanism in which the piston ring having a dimple and a cylinder having a cross hatch of large cross hatch angle at its inner peripheral surface.

This invention relates to a reciprocation mechanism 10 provided with a piston 13 having a piston ring 16 with several dimples 15 at its sliding surface and a cylinder 14 for slidably storing the piston 13 in which the cylinder 14 is constituted such that it has several cross hatch parts 18 in its axial direction including cross hatches 17 while being formed at the inner peripheral surface of the cylinder 14 with the cross hatch angle θ being in a range from 130° to 150° and a length L1, L2 in respect to the axial direction of the cylinder 14 being shorter than an entire length L0 of the cylinder 14, and a length L1 of each of the cross hatches 17 at an axial central part of the cylinder 14 is shorter than a length L2 of the cross hatches 17 at both axial ends.