To provide a part fitting structure capable of preventing a fall-out when fitting a projecting part of a part to a fitting recessed part of a member for fitting of the part.

A lock part 1d is formed at a position separated from the projecting part 1a, and the member 15 for fitting of the part is formed with a recessed part 15b for fitting of the projecting part 1a, and the lock part 1d is locked with a lock member 30a to connect the member 15 for fitting of the part to the part 1. It is necessary for the projecting part 1a to move on an arc around the lock position A to get out of the recessed part 15b. A distance r2 from the lock position A to a point C of the projecting part separated farthest from the lock position A is formed larger than a distance r1 from the lock position A to a point B of the recessed part inlet separated farthest from the lock position A to prevent a fall-out of the projecting part 1a from the recessed part 15b.