To highly precisely judge whether a print pattern is normal or abnormal without being affected by the noise of a background part by judging the pattern only by the part of a character being essential information and using an integrated sum of the density.

A picture containing the print pattern being an inspection object is inputted through a television camera (#1). It is converted into picture data of a digital type through an A/D converter (#2) and it is stored in a picture memory (#3). The circumscribing rectangle of the character mark pattern is obtained (#4). Then, the total sum of a difference with the prescribed density level is calculated (#5) only on the area whose density is lower (or higher) than a prescribed density level in picture data in the picture memory. Then, the print pattern is judged to be normal or not by using the calculated density different sum. Since pattern is judged only on the character part and by using the integrated difference sum of density, the influence of the noise of the background part is not given.