An electric operator device (1) for opening and closing a window (2) with pivotal sash (5) and comprising an operator housing (4) designed to be fastened to the frame (3) of the window, preferably to the top member thereof, said operator housing having a built-in drive motor in transmission connection with an operating member (6), which in the closed position of the window is accommodated in the operator housing (4), and a mounting bracket (9) for connecting the operating member (6) with an operating means (7), connected with the sash of the window, preferably the top member thereof. The window (2) can, in the closed position and affected by said operating means (7), be locked by engagement between locking means (11) in connection with the sash (3), preferably the top member thereof, and a strike plate (8) fastened to the frame (5), preferably to the top member thereof. The electric operator device is characterized in that the operator housing (4) comprises a strike plate (8) which is fixedly positioned relative to the frame (3) by means of co-operating positioning means (13, 16, 17) arranged on the frame (3) and the strike plate (8).