PURPOSE: To improve defectiveness detecting precision, by conducting inspection by using a different inspection condition set at every lane or block.

CONSTITUTION: At a memory means 60, optimum inspection condition sets used at every lane, I, II,....VI are memorized. A scanning lane discrimination means 64 discriminates which lane a scanning position on a main scanning line 32 is in. A selecting means 66, when a lane signal β is 'I', selects an inspec tion condition set I opposing this lane I from the means 60. Also, when the signal β becomes 'II', the means 60 selects an inspection condition II. Thus, inspection conditions I, II - VI to be selected are changed in opposition to the scanning position being changed to respective lanes I, II - V. A changeover means 68 delivers to respective portions inspection conditions selected by means of the means 66 by conducting reading from the means 60.