To provide a motorcycle assist device for raising up a motorcycle when it topples, capable of raising up even in case it is very difficult for the rider to raise up by himself.

The assist device of the motorcycle is structured so that an emergency shaft 2 of screw type is installed in a swing arm pivot shaft 3 having large diameter of the motorcycle body, and when the motorcycle has toppled down, the emergency shaft 2 is turned from an opposite side swing arm pivot part which has tumbled using a manual handle 9 accommodatable behind a seat etc. and a joint shaft 8 and is pushed out to the road surface, which enables raising up the toppled motorcycle by means of three-point support with the grounded front and rear wheels as fulcra, and thereafter it is possible to easily raise the motorcycle to the upright attitude by the rider alone with a minor force. Owing to the built-in type in the motorcycle body, this does not constitute any obstacle nor impair the outside appearance.