To prevent the parking brake force from decreasing along with the reduction in shaft load shifting amount while the driver leaves vehicle in a shaft load adjusting device for the vehicle, which is provided with an actuator to shift the load acted on a driven shaft to the side of the drive shaft of the rear section of a car body between the drive shaft and the driven shaft when necessary.

In a vehicle provided with a drive shaft 2 and a driven shaft 3 in the rear section of a car body 1, an air spring 8, which pushes down the side of the drive shaft 2 or pushes up the side of the driven shaft 3 in relation to the car body 1 and a solenoid valve 12, which supplies and discharges the compressed air of the air spring, are provided, and a main switch 13 and a detection switch 14, which turns on when the driver sit down on the seat, are provided in series on an electric source circuit of the solenoid valve. A pressure switch is provided in the seat section 15a of the driver's seat as the detection switch 14 of the driver's seat.