An image pickup apparatus includes a mount portion, a lock member movable between a lock position for locking the interchangeable lens unit and an unlock position for unlocking it, and forced from the unlock position toward the lock position, an operation member movable from a nonoperation position to an operation position in response to a press operation for moving the lock member from the unlock position to the lock position, and an interlock member movable by the pressed operation member and configured to move the lock member from the lock position to the unlocked position. The interlock member includes a contact portion configured to contact a contacted portion provided on either the lock member or a member configured to move integrally with the lock member, and at least one of the contact portion and the contacted portion has a convex shape toward the other.