To hold both of brake auxiliary force by a brake booster and air conditioning performance by an air conditioner in excellent states, in a vehicle with a brake booster utilizing intake negative pressure of an engine.

When an operation switch of the air conditioner 13 is turned on, negative pressure of a communicating passage 8 for connecting the brake booster 1 of the vehicle and an intake pipe 6 of the engine 5 is detected to be below a prescribed value by a negative pressure switch 10, the stopping of the traveling vehicle is detected by a speed sensor 15 and the operation of a brake 12 is detected by a brake switch 16. At the time, a controller 14 stops the operation of the air conditioner 13 by prescribed time from the stopping time and operates the air conditioner 13 after the lapse of the prescribed time.