To exhibit excellent ride comfort and turning characteristic by cutting off transmission to a saddle of vibration of right and left rear wheels received from the road surface, and by making so that the right and left rear wheels always simultaneously elevate with respect to a vehicle body frame in a three-wheel type power-assisted bicycle.

A swing arm 20 mutually integrally connecting a pair of right and left rear forks 22, 22 supporting right and left rear wheels 10r, 10r is vertically oscillatably connected through a pivot shaft 26 to a rear part of the vehicle body frame F supporting a saddle 15, and the distance between the vehicle body frame and the swing arm 20 is connected through a cushion member 30 elastically deformed according to the vertical oscillation of the swing arm 20 in the three-wheel type power-assisted bicycle.