A direction switchable ratchet device for a door operator is provided. The door operator includes an electric motor, an electromagnetic brake and the direction switchable ratchet device. The direction switchable ratchet device comprises a first and second direction restricting devices and a manually operable mechanism. A drive shaft of the electric motor is braked by a brake baffle disk when the electric motor is electrically de-energized and is released when the electric motor is electrically energized. The first and second direction restricting devices are provided to prevent the drive shaft from being rotated clockwise and counter-clockwise respectively by holding the brake baffle disk. In the event of power failure, the manually operable mechanism is effective to open the door once a pawl of the direction restricting device at the free side is retracted. The manually operable mechanism of the door operator is prevented from being incorrectly mounted in a cost-effective manner.