To enable traveling maintaining a vehicle speed suitable for a vehicle and prevent wasteful consumption of a battery by reducing electric drive force (drive force of a motor) in a high vehicle speed range, and prevent uncomfortable vibration to a vehicle body to comfortably travel even when driving with rapid increase of the vehicle speed, in a control method for the vehicle with a motor assist function provided with a human power drive system and an electric drive system in parallel, controlling the electric power drive force correspondingly to the human power drive force on the basis of a previously stored assist rate characteristic.

The assist rate characteristic is set to a high speed gradual reduction characteristic bending at a set vehicle speed, while a control fluctuation width of the electric power drive force is corrected to be smaller than a control fluctuation width according to the assist rate characteristic when the vehicle speed is above the set vehicle speed. A control device comprises a microcomputer, and can correct a current command value such that a fluctuation width of a current command value gotten every prescribed calculation cycle time of the computer becomes a predetermined value or less.