Abstract: A connector fitting detection construction in which even if dirt, dust or the like is deposited on contacts, the contacts can be positively electrically connected together, thereby enhancing the reliability of a fitting detection function. In the connector fitting detection construction for detecting a fitted condition of a pair of connectors, a cantilever-like lock arm is provided on one connector housing, and the lock arm can be elastically flexed so that its free end can be moved in a direction generally perpendicular to a connector fitting direction. A short-circuiting electrode of a U-shape, having contact portions provided respectively on outer sides of pair of legs, is mounted on the lock arm, with the pair of legs disposed respectively on opposite sides of the lock arm.