To provide a cover member mounting structure easy in manufacturing.

A pin insert hole 4 is formed in a housing 1. An end side small diametral part 5 and a large diametral part 6 engaged with a cover member 2 are formed in a mounting pin 3 inserted in the pin insert hole 4, and a stepped part 7 having larger diameter than the inside diameter of the pin insert hole 4 is formed between these small diametral part 5 and the large diametral part 6. The mounting pin 3 is inserted in the pin insert hole 4 of the housing 1 and the opening end of the pin insert hole 4 is plastically deformed by the stepped part 7 of the mounting pin 3 so as to be contracted, thereby the cover member 2 can be attached to the housing 1.