A manual window regulator in which a pinion rotatably carried by a window glass and driven by a manual handle is held in engagement with a rack which is fixed to extend in the direction of movement of the window glass, so that a manual rotation of the handle causes the pinion to roll along the rack in meshing engagement therewith so as to drive the window glass thereby opening and closing a window. The transmission of rotation from the handle to the pinion is effected through a tape stretched between a drive gear rotationally driven by the handle and driven gear coaxially fixed to the pinion. The rack and the pinion are usable also as the parts of a power window regulator. The manual window regulator therefore can be easily converted into a power window regulator by using an electric motor for driving the pinion in place of the unit including the handle, the drive gear and the tape.