To easily mount and detach a battery part below a main pipe.

In a motor-assisted bicycle provided with an electric motor for driving wheels and a battery part 31 as a driving power source for the electric motor, a battery placing table 17 is rotatably provided in the position lower than the connecting parts of a vertical pipe 2 and the main pipe 3 by taking the vertical pipe 2 as a shaft, the battery part 31 is placed on the battery placing table 17, and the battery part 31 is arranged below the main pipe 3 by the turning movement of the battery placing table 17.