To provide a cylinder device capable of maintaining excellent joining conditions.

The device has a tubular cylinder 101, an end member 102 to be press-fit into the end side of the cylinder 101, and a welded part 103 where the cylinder 101 and the end member 102 are fixed by welding. There are provided abutting parts 108 abutting on the cylinder 101 and notch parts 107 alternately in a circumferential direction of the end member 102. The welded part 103 communicates with an internal space 114 of the cylinder 101 through the notch parts 107. This inhibits generation of blow holes in the welded part 103.