A connector apparatus includes a housing having an upper surface portion formed with an accommodation space, and a position assurance to be inserted into the accommodation space of the housing. When the position assurance is mounted in the housing, a mounting portion of the position assurance is exposed on a side surface portion of the housing, such that visibility at the time of work is improved. In addition, the position assurance is connected to the housing in a catching structure, such that it is easy to mount and demount the position assurance and mounting strength is secured.