An electric assist bicycle is provided with a so-called single-shaft motor drive unit that can satisfactorily keep torque detection capability. The outer periphery of a crank shaft 7a has a cylindrical human power transmission member 28 having a torque sensor 31 for detecting a human driving force and a combined-force member 29 that combines a human driving force and an auxiliary driving force from a motor 21. A one-way clutch is not provided on a driving force transmission path including the crank shaft 7a, the human power transmission member 28, and the combined-force member 28. The human power transmission member 28 and the combined-force member 29 are always rotated in response to a rotation of the crank shaft 7a. Moreover, a rotation detector 10 is provided to detect a rotation of the combined-force member 29.
