Shock absorber and method of manufacturing the shock absorber

A shock absorber, comprising:

• a first cylindrical body formed in a cylindrical shape;
• a second cylindrical body surrounding an outer peripheral surface of the first cylindrical body and provided movably in a direction of an axis of the first cylindrical body with respect to the first cylindrical body;
• a spring provided between the outer peripheral surface of the first cylindrical body and an inner peripheral surface of the second cylindrical body and applying a force in a direction of separating the first cylindrical body and the second cylindrical body;
• and
• a spring seat portion that is a cylindrical body provided between the outer peripheral surface of the first cylindrical body and the inner peripheral surface of the second cylindrical body and supporting an end portion of the spring in the axis direction, the spring seat portion being made of resin and being arranged movably in a direction intersecting the axis direction, wherein
• the spring seat portion includes a first cylindrical portion having a cylindrical shape and supporting the end portion of the spring, a second cylindrical portion having a cylindrical shape and continuously extending from the first cylindrical portion toward a side opposite to the spring, a groove located on an outer peripheral surface of the spring seat portion and extending from a tip end surface of the second cylindrical portion toward a tip end surface of the first cylindrical portion, and a through hole positioned at a bottom of the groove and formed in the first cylindrical portion in a direction intersecting an axis of the spring seat portion,
• an outer diameter of the second cylindrical portion is smaller than an outer diameter of the first cylindrical portion,
• an inner diameter of the second cylindrical portion is smaller than an inner diameter of the first cylindrical portion, and
• an inner peripheral surface of the second cylindrical portion has a curved surface portion of which an inner diameter increases as it approaches the first cylindrical portion.