To prevent wrong judgments at the time of dirt inspection of packages and improve dirt inspection accuracy, by removing shadows of bunching threads, thread ends, etc., from the dirt inspection of packages.

A line sensor d2 generates a voltage signal upon receipt of a reflecting light generated when light beams from a light source d1 are reflected at an end face p1 of a package P. The voltage signal generated by the line sensor d2 becomes different in fall depth and fall width depending on whether it is a thick dirt s1, a wide dirt s2 or a bunching tread y1. A fall of the voltage signal of the line sensor d2 is judged by an operation apparatus C based on the voltage signal in the case of the bunching thread y1 as a reference. The thick dirt s1 and wide area dirt s2 which are necessary to eliminate as a defective package are distinguished from a shadow of the bunching thread y1, and therefore only the defective package required to be eliminated is surely eliminated and the shadow resulting from the bunching thread y1 is prevented from being judged wrong as a dirt.