A connector, comprising: at least one terminal fitting; a connector housing including at least one cavity into which the terminal fitting is to be at least partly inserted, at least one locking lance for locking and retaining the terminal fitting being resiliently deformable formed to project at the cavity; and a retainer to be mounted into the connector housing and configured to restrict resilient deformation of the locking lance to lock the terminal fitting by being at least partly inserted into a deformation space for the locking lance when the terminal fitting is properly inserted in the cavity and, on the other hand, come into contact with the resiliently deformed locking lance to prevent any further insertion of the retainer when the terminal fitting is in an insufficiently inserted state in the cavity; wherein at least one first contact portion with which the retainer comes into contact when the terminal fitting is in the insufficiently inserted state in the cavity and at least one second contact portion with which a jig for releasing a locked state of the terminal fitting can come into contact are respectively provided at different positions of the locking lance; the retainer includes an insufficient insertion detecting portion which comes into contact with the first contact portion when the terminal fitting is in the insufficiently inserted state in the cavity; the first contact portion comprises a contact surface and the insufficient insertion detecting portion comprises a retainer-side contact surface, both contact surfaces (34, 62) being inclined with respect to a mounting direction of the retainer into the the connector housing, such that the retainer-side contact surface can slide on the contact surface of the first contact portion, whereby the locking lance is resiliently deformed into the deformation space; and characterized in that the second contact portion is provided in a widthwise intermediate or central part of the locking lance, the insufficient insertion detecting portion is provided on a lateral part of the retainer, and a widthwise intermediate or central part of the leading end portion of the retainer is cut to form a recess for avoiding interference with the second contact portion, and the first and second contact portions (31, 32) are shifted from each other in a direction perpendicular to the mounting direction of the retainer into the connector housing. at least one terminal fitting; a connector housing including at least one cavity into which the terminal fitting is to be at least partly inserted, at least one locking lance for locking and retaining the terminal fitting being resiliently deformable formed to project at the cavity; and a retainer to be mounted into the connector housing and configured to restrict resilient deformation of the locking lance to lock the terminal fitting by being at least partly inserted into a deformation space for the locking lance when the terminal fitting is properly inserted in the cavity and, on the other hand, come into contact with the resiliently deformed locking lance to prevent any further insertion of the retainer when the terminal fitting is in an insufficiently inserted state in the cavity; wherein at least one first contact portion with which the retainer comes into contact when the terminal fitting is in the insufficiently inserted state in the cavity and at least one second contact portion with which a jig for releasing a locked state of the terminal fitting can come into contact are respectively provided at different positions of the locking lance; the retainer includes an insufficient insertion detecting portion which comes into contact with the first contact portion when the terminal fitting is in the insufficiently inserted state in the cavity; the first contact portion comprises a contact surface and the insufficient insertion detecting portion comprises a retainer-side contact surface, both contact surfaces (34, 62) being inclined with respect to a mounting direction of the retainer into the the connector housing, such that the retainer-side contact surface can slide on the contact surface of the first contact portion, whereby the locking lance is resiliently deformed into the deformation space; and characterized in that the second contact portion is provided in a widthwise intermediate or central part of the locking lance, the insufficient insertion detecting portion is provided on a lateral part of the retainer, and a widthwise intermediate or central part of the leading end portion of the retainer is cut to form a recess for avoiding interference with the second contact portion, and the first and second contact portions (31, 32) are shifted from each other in a direction perpendicular to the mounting direction of the retainer into the connector housing.