A mechanism for raising and lowering a windowpane achieves a satisfactory mounting of a guide rail to a drum housing to allow visual checking of the mounted state of the guide rail to the drum housing. Relative movement between the guide rail and the drum housing is restricted in the vehicle widthwise direction after completion of the mounting. An engaging projection formed at the end of the drum housing projects toward the guide rail. An engaging portion of the guide rail restricts relative movement between the guide rail and the drum housing in the vehicle widthwise direction by being engaged with the engaging projection.