To determine whether a situation needs a warning, and the warning is issued if needed.

In a method of controlling a coaxial two wheeler, a traveling speed is controlled based on a tilting angle of a vehicle body and a handle coupled with the vehicle body, and when the traveling speed detected by a detecting device exceeds a prescribed speed, an occupant is warned. When a travel direction of the coaxial two wheeler is a positive direction, and the traveling speed exceeds a prescribed speed, and when the tilting angular velocity of the handle is a positive direction, a warning is issued, and when the tilting angular velocity of the handle is a negative direction, a warning is stopped.