An apparatus for confirming the fitting of an electric connector in which a male connector housing is fitted in a hood of a female connector housing so as to connect together metal terminals received respectively in the terminal receiving chambers of the male and female connector housings. A lock lever, having a holder spring, is pivotally connected at one end to a first side portion of the hood. A locking plate, having a provisional locking groove and a complete locking groove, is formed on a second side portion of the hood. Both the provisional and complete locking grooves are engageable with the holder spring. A fitting confirmation projection is formed on a reverse surface of the lock lever, and interferes with the male connector housing when the fitting of the male connector housing is imperfect, thereby preventing the engagement between the holder spring and the complete locking groove. The apparatus also may be used when a hood of a female connector housing is fitted in an electronic unit case so as to provide an open window in the electronic unit case. In this embodiment, a manipulation press portion is formed on a second end of the lock lever. Additionally, a screen portion is formed on the press portion so as to close the window in the electronic unit case to prevent foreign matter from penetrating the electronic unit case.