An electric bicycle comprising: a plurality of wheels (3, 4); a frame; and a driving unit that includes a motor, the electric bicycle being configured to travel with a combination of human driving force generated by pedal force applied from pedals and auxiliary driving force generated by the motor, and to transmit passive rotational force to the motor for regeneration, the passive rotational force being applied to the plurality of wheels (3, 4) from a contact surface, wherein one wheel of the plurality of wheels is provided with a hub device (50, 50A) including: a hub shaft attachable to the frame; a hub body rotatable around the hub shaft, and rotatable with the one wheel as a one-piece body; a rotation wheel body that outputs the passive rotational force to the driving unit; and a passive rotational force speed reduction transmission path (X2, X2a) at which a speed of the passive rotational force transmitted to the hub body is reduced to a speed lower than a rotation speed of the hub body and the passive rotational force having the reduced speed is transmitted to the rotation wheel body, characterized in that the driving unit is attached with an auxiliary driving force output wheel body that outputs the auxiliary driving force, the electric bicycle includes a passive rotational force motor transmission path through which the passive rotational force is transmitted from the auxiliary driving force output wheel body to the motor, the driving unit further includes a speed reduction mechanism which transmit the passive rotational force to the motor, the passive rotational force is transmitted to the motor via the hub device (50, 50A), a rear sprocket, a chain, a front sprocket, a resultant force transmitter and the speed reduction mechanism, the speed reduction mechanism includes an intermediate shaft, a speed reduction gear, a first intermediate shaft speed reduction gear, a second intermediate shaft speed reduction gear, and a motor shaft speed reduction gear, and the first and second intermediate shaft speed reduction gears (37, 38) rotate with the intermediate shaft as a one-piece body. a plurality of wheels (3, 4); a frame; and a driving unit that includes a motor, the electric bicycle being configured to travel with a combination of human driving force generated by pedal force applied from pedals and auxiliary driving force generated by the motor, and to transmit passive rotational force to the motor for regeneration, the passive rotational force being applied to the plurality of wheels (3, 4) from a contact surface, wherein one wheel of the plurality of wheels is provided with a hub device (50, 50A) including: a hub shaft attachable to the frame; a hub body rotatable around the hub shaft, and rotatable with the one wheel as a one-piece body; a rotation wheel body that outputs the passive rotational force to the driving unit; and a passive rotational force speed reduction transmission path (X2, X2a) at which a speed of the passive rotational force transmitted to the hub body is reduced to a speed lower than a rotation speed of the hub body and the passive rotational force having the reduced speed is transmitted to the rotation wheel body, characterized in that the driving unit is attached with an auxiliary driving force output wheel body that outputs the auxiliary driving force, the electric bicycle includes a passive rotational force motor transmission path through which the passive rotational force is transmitted from the auxiliary driving force output wheel body to the motor, the driving unit further includes a speed reduction mechanism which transmit the passive rotational force to the motor, the passive rotational force is transmitted to the motor via the hub device (50, 50A), a rear sprocket, a chain, a front sprocket, a resultant force transmitter and the speed reduction mechanism, the speed reduction mechanism includes an intermediate shaft, a speed reduction gear, a first intermediate shaft speed reduction gear, a second intermediate shaft speed reduction gear, and a motor shaft speed reduction gear, and the first and second intermediate shaft speed reduction gears (37, 38) rotate with the intermediate shaft as a one-piece body. a hub shaft attachable to the frame; a hub body rotatable around the hub shaft, and rotatable with the one wheel as a one-piece body; a rotation wheel body that outputs the passive rotational force to the driving unit; and a passive rotational force speed reduction transmission path (X2, X2a) at which a speed of the passive rotational force transmitted to the hub body is reduced to a speed lower than a rotation speed of the hub body and the passive rotational force having the reduced speed is transmitted to the rotation wheel body, characterized in that the driving unit is attached with an auxiliary driving force output wheel body that outputs the auxiliary driving force, the electric bicycle includes a passive rotational force motor transmission path through which the passive rotational force is transmitted from the auxiliary driving force output wheel body to the motor,