Electric power assisted bicycle

To obtain an electric power assisted bicycle capable of efficiently applying an input torque by a motor to a pedaling force. [Means for solving the object] An electric power assisted bicycle comprises a pedaling force sensor (2) for detecting the pedaling force generated on a pedal, a motor (5) for assisting a driving force in response to an output of the pedaling force sensor (2), a crank angle sensor (3) for detecting a crank angle of a crankshaft connected to the pedal, a crank rotational frequency calculating means (14) for calculating a rotational frequency of the crankshaft from the crank angle, and an assist amount control section (10) for allowing the motor (5) to generate a driving force assist amount configured relative to the pedaling force (a rotation torque value f of the crankshaft) detected by the pedaling force sensor (2), in response to a phase of the crank angle detected by the crank angle sensor (4) when the crank rotational frequency calculated through the crank rotational frequency calculating means (14) is not less than a predetermined value.