To provide a self-traveling prevention device for a motor-assisted vehicle, capable of restricting supply of assist power to a short time when a command current is large, and reducing a self-traveling time.

In the motor-assisted vehicle, the assist power according to pedaling force of a rider is generated in a drive motor and is supplied as rear wheel drive force. The motor-assisted vehicle has an abnormal state detection part 25 detecting an abnormal state unable to properly detect the pedaling force of the rider; an abnormal state time measurement part 26 measuring an elapsing time of the abnormal state detected by the abnormal state detection part 25; a command current integration part 27 integrating the command current to the drive motor every unit time when measuring the elapsing time; and a supply restriction part 29 restricting the supply of the assist power on the basis of a signal from the command current integration part 27 when the command current integration value exceeds a prescribed value.