When the center of gravity of the load put on the two prongs of a forklift is located to the right or left of the central position, the prongs are tilted. The invention is intended to prevent the prongs from tilting in this situation. Tilt sensors are mounted on the prongs. A computer calculates the tilt angles of the prongs, based on the output signals from the sensors. A driving device receives the output signals from the computer and brings the prongs into the horizontal.