To prevent fluctuation of maneuvering stability when an abnormal condition is generated in vehicle characteristic alteration control for maintaining vehicle maneuvering stability in a braking force controller by which brake assist control generating intensive braking force as against an ordinary time is carried out when an emergency brake is required in a vehicle.

When an abnormal condition is detected in vehicle characteristic alteration control in any one step among steps 102, 106-114, a boosting grade for a rear wheel in brake assist control is reduced in the step 104. When the boosting grade for the rear wheel is reduced, maneuvering stability for a vehicle is improved. Therefore, fluctuation in maneuvering stability due to execution of the brake assist control can be prevented when an abnormal condition is caused in the vehicle characteristic alteration control.