PURPOSE: To detect a collision between moving bodies with a small calculation quantity without overlooking by recursively repeating a decision on decision conditions regarding a collision and the halving of a track.

CONSTITUTION: A system consists of an IBM 5080 graphic system 1 and an IBM RT-PC personal computer 2 and is equipped with a minimum distance calculation part 5, a maximum movement length calculation part 6, a collision presence/absence decision part 7, and an end condition decision part 8. Here, when the condition that the minimum distance between two bodies at the start or end of movement is larger than the sum of the 'maximum movement lengths' of the two bodies is met, the principle that the two bodies never collide against each other is utilized. When the condition is not met, the track is divided and the condition is checked again as to the small tracks obtained by the division; and this procedure is recursively followed to detect a collision. Consequently, a collision can be detected with a small calculation quantity without being missed.