An optical connector plug, comprising: a front housing, configured to hold a ferrule and to be fitted with a fitting portion of a coupling counterpart member; and a rear housing, mounted to the front housing so as to be allowed to slide toward front and rear directions at a rear side of the front housing, wherein the front housing comprises: a front housing body; and a latching piece with elasticity, formed on an upper side outer wall face of the front housing body, the latching piece comprises: a locking portion, configured to engage with an engaging portion for fitting of the coupling counterpart member; a releasing portion, configured to release the locking portion from an engaging state with the engaging portion for fitting, wherein the releasing portion has a sloping face formed at a front side of the releasing portion so that the sloping face has a lower front end and a higher rear end, and a slit formed in front of the sloping face the rear housing comprises: a tubular body; and a releasing lever, formed at an upper side of the tubular body, the releasing lever comprises: a hook portion, formed at a front part of the releasing lever and configured to engage with the releasing portion of the latching piece at a time of retreat of the rear housing, so as to activate a release function, and having a taper portion formed at a distal end side of the hook portion; and a knob portion for retreat, formed at a rear part of the releasing lever, and the hook portion formed at the releasing lever loosely fits with the slit formed before the releasing portion, by the hook portion sliding with and entering under the releasing portion of the latching piece, the taper portion at a distal end side of the hook portion pushing up the releasing portion and the hook portion entering into the slit when the front housing and the rear housing are assembled, wherein the knob portion is adapted to be pulled backward to move the rear housing backward after the optical connector plug is coupled with the coupling counterpart member, the rear housing slides backward relatively to the front housing, so that a rear end of the hook portion loosely fitted in the slit engages with the sloping face of the releasing portion, and slides backward on the sloping face, which allows the releasing portion to be pressed down against the elastic force of the latching piece, resulting in that engagement of the locking portions with the engaging portion of the coupling counterpart member is released. a front housing, configured to hold a ferrule and to be fitted with a fitting portion of a coupling counterpart member; and a rear housing, mounted to the front housing so as to be allowed to slide toward front and rear directions at a rear side of the front housing, a front housing body; and a latching piece with elasticity, formed on an upper side outer wall face of the front housing body, a locking portion, configured to engage with an engaging portion for fitting of the coupling counterpart member; a releasing portion, configured to release the locking portion from an engaging state with the engaging portion for fitting, wherein the releasing portion has a sloping face formed at a front side of the releasing portion so that the sloping face has a lower front end and a higher rear end, and a slit formed in front of the sloping face a tubular body; and a releasing lever, formed at an upper side of the tubular body, a hook portion, formed at a front part of the releasing lever and configured to engage with the releasing portion of the latching piece at a time of retreat of the rear housing, so as to activate a release function, and having a taper portion formed at a distal end side of the hook portion; and a knob portion for retreat, formed at a rear part of the releasing lever, and the hook portion formed at the releasing lever loosely fits with the slit formed before the releasing portion, by the hook portion sliding with and entering under the releasing portion of the latching piece, the taper portion at a distal end side of the hook portion pushing up the releasing portion and the hook portion entering into the slit when the front housing and the rear housing are assembled, wherein the knob portion is adapted to be pulled backward to move the rear housing backward after the optical connector plug is coupled with the coupling counterpart member, the rear housing slides backward relatively to the front housing, so that a rear end of the hook portion loosely fitted in the slit engages with the sloping face of the releasing portion, and slides backward on the sloping face, which allows the releasing portion to be pressed down against the elastic force of the latching piece, resulting in that engagement of the locking portions with the engaging portion of the coupling counterpart member is released.