A connector fitting construction in which a half-fitted condition is positively prevented when fitting a pair of male and female connectors together, and the fitting operation and a fitting release operation can be effected easily, and a connector housing can be formed into a small size. In this connector fitting construction, the male connector includes a connector housing, and an exclusive-use housing forming a slider receiving portion for receiving a slider therein. Guide grooves for respectively guiding opposite side portions of a body of the slider are formed respectively in opposite side portions of the exclusive-use housing. A lock arm, provided at a central portion of the exclusive-use housing, includes a lock beak having a slanting surface, and a housing lock formed on a lower surface thereof at a front end thereof, and side spaces are provided respectively on opposite sides of the lock arm. The slider has a slider arm provided in the slider body, the slider arm having a pair of abutment projections. The female connector includes a pair of stopper projections, which are formed on a housing, and abut respectively against the abutment projections when the two connectors are fitted together, a slanting projection having a slanting surface, and an engagement groove.