PURPOSE: To automate handling by providing a laser light source and a reflection light receive camera on a trolley, computing the reflection point position from its positional relation, changing the direction of light continuously by a mirror to scan over the total length, and detecting the position of load accurately.

CONSTITUTION: A laser light source 1 and a camera which receives its reflected light are provided on a crane trolley 8, and a mirror 12 which changes the direction of light projection from the light projection source continuously is provided. When the trolley 8 comes above a container 6, the mirror 12 rotates or reciprocates, and laser light from the light source is reflected up to both ends F, F of the container 6. Its reflected light is caught by the camera 2 and input into a processing unit 9, and the position of reflection coalescence point is computed. Consequently, the position of the container 6 can be detected accurately, and handling to the container can be facilitated and automated.