A cylinder chamber filled with a liquid, a piston disposed inside the cylinder chamber, a piston rod connected to the piston, and an accumulator allowing the piston rod to generate a damping force by receiving the liquid from a compression side of the cylinder chamber are included, and on an internal periphery of the cylinder chamber, one line of a helical damping groove is formed within a stroke range of the piston, a groove width of the damping groove is constant over the entire length of the damping groove, a depth of the damping groove gradually decreases along a spiral toward the direction in which the piston rod is pushed in, and a length of the piston in a direction along the axis line is smaller than a pitch of the damping groove.