To provide a strap mounted part where a strap can easily be mounted.

A projection part 10 of the strap mounted part 7 is run through one end part 20a of the strap 20 which is looped and in this state, the other end part 20a of the strap 20 is drawn. The width of a connection part 14 of the projection part 10 for a lower case 2 is less than the width of strap stopper arm parts 13 of the projection part 10. Consequently, while the drawn one end part 20a of the strap 20 moves to the position of the connection part 14 to be caught by the connection part 14, the strap is mounted on the strap mounted part 7. In this state, the diameter of the one end part 20a is reduced almost to the same size as the diameter of the connection part 14, and the one end part 20a is caught by the strap stopper arm parts 13 of the projection part 13 which protrude to the right and left, so the strap 20 does not easily fall from the strap mounted dpart 7.