PURPOSE: To provide an inspection system which prevents the inspection omission of both end chips in a foreign matter inspective device by system for comparion adjacent chips.

CONSTITUTION: When scanning with a laser beam is in the positive direction (LR) of X, the polarity of differential data of the chip at the foremost position (A) and at its following position (B) of a X-directional chip array 11X is reversed; when in the negative direction of X, the polarity of differential data of the chip at the final position (N) and at its preceding position (M) of the chip array is reversed: results are compared with the threshold value Vth of positive pole to detect foreign matters of both end chips at the foremost position (A) and the final position (N). Chips (B)-(M) other than those at both ends of the chip array have foreign matters detected as the prior art by comparing the differential data of + pole of detected data of the chip at the rear position and at the fore position with the threshold value V.. of positive pole, whereas both end chips have foreign matters detected regardless of the scanning direction of a laser beam by reversing the polarity of their differential data to-with the result that all the chips are inspected.