To provide a method which facilitates the fixing of the posture of a wheelchair having a height-adjustable seat.

The wheelchair is provided with first and second locking means for fixing the wheelchair on a predetermined position of a loading platform of a lifter. When the wheelchair is loaded onto the loading platform outside a vehicle, the first locking means is automatically locked to fix the wheelchair in the position. The wheelchair is then loaded into a vehicle with the loading platform, and the second locking means is automatically locked to fix the posture of the wheelchair by adjusting the seat height of the wheelchair to a driving position.