To provide a bracket mounting structure for cylinder device preventing cylinder deformation due to welding, and residual of foreign materials in the cylinder.

A mounting part 15 of a bracket 14 is made to abut on a side surface part of the cylinder 2 of a hydraulic shock absorber 1. A C-shape ring 18 is wound from an upper part of the mounting part 15 around the cylinder 2 with a certain interference and both ends of the C-shape ring 18 are spot- welded on the surface of the mounting part 15. Fastening the mounting part 15 and the cylinder 2 by the C-shape ring 18 with a certain interference allows the bracket 14 to be securely fixed to the cylinder 2. In this case, the bracket 14 is not directly welded to a side wall of the cylinder 2, preventing deformation of the cylinder 2 due to welding, and also preventing residual of foreign materials in the cylinder 2.