To provide a lock mechanism capable of preventing a hook part and a lock part from being deformed or damaged even if a pair of component members are engaged with or disengaged from each other, and unlocking the component members easily without using a jig.

This lock mechanism 26 installs a protector cover 23 on a protector body 22 by hooking a hook part 31b provided at the tip of a locking flexible piece 31 of a protector body 22 to a hooking part 34 provided on a protector cover 23. The hooking part 34 comprises a hook hooking part 33 hooking the hook part 31b and a disengaging hole 35 allowing the disengagement from the hook part 31b when locking flexible piece 31 is displaced elastically in the direction generally perpendicular to the direction of projection of the hook part 31b.