An acquisition section 42 acquires a pose at a clock time ti and a pose at a clock time tj for each of plural robots, and acquires structural information. Based on structural information a computation section 44 computes positions of the prescribed part for each of the robots at the clock times ti, tj and at a midway clock times tc. A possibility determination section determines a possibility of interference, based on any overlap between added-margin regions resulting from addition of a prescribed margin to a circumscribing shape containing positions of the prescribed part at the clock times ti, tj, and tc for each of the robots. In cases in which there is a possibility of interference, an end determination section 48 sets tc so as to be a new ti or a new tj, and causes processing of the computation section 44 and the possibility determination section 46 to be executed repeatedly until a spacing between the prescribed parts satisfies an end condition. When determined that the end condition has been satisfied, an interference determination section 50 determines whether or not there is interference between the prescribed parts between the robots at any of the positions at ti, tc, and tj.