A lock detecting structure of connector comprises: a male connector housing (100) formed with a deformable lock arm (105) having a lock projection (112), and with two slider stoppers (150); a female connector housing (200) mated with the male connector housing (100) and formed with a lock claw (210) engaged with the lock projection of the male connector housing, and a slider release projection (206); and a slider (300) slidable inserted into the male connector housing (100) and stopped at a temporary engage position due to engagement of the slider with the lock projection (112) and the two slider stoppers (150) of the male connector housing. When the male connector housing (200) is perfectly mated with the female connector housing (100) and thereby the slider is deformed inward away from the lock projection (112) and the slider stoppers (150) of the male connector housing by the lock claw (210) and the slider release projection (206) of the female connector housing (200), the slider can be further inserted deep into the female connector housing (200) to a lock confirmation position. In particular, since the two slider stoppers (150) are formed inside the male connector housing and therefore the slider can be stopped within the male connector housing, it is possible to reliably detect the connector housing lock conditions, without being subjected to the influence of an external force applied to the slider.