Abstract: An electric drive device for a bicycle includes a motor connected to a speed reduction device which has a bevel gear engaged with an annular gear mounted to a rotatable tube that extends through the bottom bracket of the bicycle frame. A crank axle rotatably extends through the rotatable tube with a first unidirectional device connected between the crank axle and the rotatable tube. The annular gear has a plurality of notches defined in the inside thereof and a second unidirectional device is connected between the annular gear and the rotatable tube. The second unidirectional device has a socket with a plurality of pawls pivotally connected thereto which are engaged with the notches when the motor is actuated to drive the rotatable tube while the first unidirectional device releases the connection between the crank axle and the rotatable tube.