An electric bicycle that assists a driving force generated by rotating pedals with human power, with an auxiliary driving force generated by a motor, the electric bicycle comprising: a pedal force detector that detects a pedal force applied to the pedals; a motor including a rotor, the motor rotating, when the pedal force detector detects that the pedal force is not smaller than a predetermined force, the rotor and an output rotation unit rotated by the rotor so as to generate the auxiliary driving force on a wheel; a clutch that is disengaged to interrupt power transmission between the output rotation unit and the wheel when the output rotation unit rotated by the rotor has a rotation speed lower than a rotation speed of the wheel, and is engaged to transmit the auxiliary driving force to the wheel from the output rotation unit when the rotation speed of the output rotation unit rises to the rotation speed of the wheel; a wheel speed detector that detects the rotation speed of the wheel; characterized by a rotation speed detector that detects a rotation speed of one of the output rotation unit and the rotor corresponding to the output rotation unit; and a rotation controller that rotates, when the pedal force detector detects that the pedal force is not smaller than the predetermined force, the output rotation unit at least at a predetermined first acceleration if the rotation speed of the output rotation unit is not lower than the rotatio speed of the wheel based on detected values of the wheel speed detector and the rotation speed detector, and rotates, if the rotation speed of the output rotation unit is lower than the rotation speed of the wheel, the output rotation unit at a second acceleration lower than the first acceleration when at least the clutch is engaged. a pedal force detector that detects a pedal force applied to the pedals; a motor including a rotor, the motor rotating, when the pedal force detector detects that the pedal force is not smaller than a predetermined force, the rotor and an output rotation unit rotated by the rotor so as to generate the auxiliary driving force on a wheel; a clutch that is disengaged to interrupt power transmission between the output rotation unit and the wheel when the output rotation unit rotated by the rotor has a rotation speed lower than a rotation speed of the wheel, and is engaged to transmit the auxiliary driving force to the wheel from the output rotation unit when the rotation speed of the output rotation unit rises to the rotation speed of the wheel; a wheel speed detector that detects the rotation speed of the wheel; a rotation speed detector that detects a rotation speed of one of the output rotation unit and the rotor corresponding to the output rotation unit; and a rotation controller that rotates, when the pedal force detector detects that the pedal force is not smaller than the predetermined force, the output rotation unit at least at a predetermined first acceleration if the rotation speed of the output rotation unit is not lower than the rotatio speed of the wheel based on detected values of the wheel speed detector and the rotation speed detector, and rotates, if the rotation speed of the output rotation unit is lower than the rotation speed of the wheel, the output rotation unit at a second acceleration lower than the first acceleration when at least the clutch is engaged.