A wind-powered brake system which is operated to brake a movable body when a driving force of a driving source for moving the movable body should be decreased, is described. The object of the present invention is to assist normal braking, to reduce a heat energy loss, and to perform braking suitable for a necessary braking force.A wind tunnel 34 is installed in each armrest 16 of a wheelchair 10. In braking, a load for generating power is put on rotary vanes 40 provided in the wind tunnel 34. Thus, the flow of wind is obstructed, and this functions as a braking force. It is thus possible to brake the wheelchair 10 using a combination of a brake mechanism of an electric motor and a wind-powered brake system. The burden on the brake mechanism of the electric motor can be lessened, and early wear and performance degradation due to frictional heat can be suppressed. By assisting the brake function of the electric motor, the amount of heat energy released from the electric motor into the air can be reduced. The generated power can be utilized to charge a battery 32, and the continuous mileage of the wheelchair 10 can be increased.