To measure the stereoscopic shape of the load top surface in a short time without degrading measuring accuracy.

Wherever a load top surface is positioned at any height within an assumed range from the height of the load on the highest stage to the height of a pallet on the lowest stage, the height of the load top surface is measured at one or more initial slit light projecting angles at which slit light 5 is always irradiated to the load top surface, and any of image data signals from a close- range image pickup device 9a and a long-range image pickup device 9b is selected based on the measured results of the height of the load top surface. After light projection is conducted while the slit light 5 is being projected to the load surface at a slit light projecting angle for actual measurement, and the shape of the load top surface is measured using the selected image data signal, then the cargo 2 to be loaded or unloaded is recognized from the shape of the load top surface.