Provided is a cylinder apparatus capable of obtaining optimum valve characteristics. The cylinder apparatus has an annular valve member provided with at least a part of flow paths and having a through-bore, a pin member inserted through the through-bore of the valve member, and an annular disk valve having the pin member inserted therethrough and movable at both inner and outer peripheries thereof selectively away from and into contact with one end surface of the valve member to open and close the flow paths, respectively. The valve member has a projecting portion around the through-bore on the one end surface. The projecting portion is locally provided with circumferentially spaced grooves. The disk valve has small-diameter portions extending toward the grooves from the inner periphery thereof. The small-diameter portions are slidable relative to the pin member.