A rotor member in a locking device is rotatably supported in a base member, is connected to a locking member by projecting to the back side from an opening portion formed in a mounting seat face, and drives the locking member in accordance with the operation of an operating member. A first locating portion of the base member abuts or is near an edge portion of the opening. A second locating portion is inserted into a locating hole formed in an opening and closing member. The first locating portion projects further toward the back side than the second locating member.