To make it possible to discriminating the abnormality of article and noise and to prevent the influence of disturbance by incorporating a step for digitizing analog data and a step for judging the propriety of a sensory characteristic curve as well as the propriety of the article.

The sensory characteristic curve by the analog data detected by a sensory sensor is image-processed, coordinate-divided with the number of lines according to the image resolution, for example, 512 lines in X- and Y-axis directions, and digitized. Then, the X- and Y-axis coordinate data of the digitized analog data are compared with the corresponding reference data of non-defective article, and the conformity of both the data is judged by fuzzy inference. The propriety of the sensory characteristic curve is judged by the judgment over the entire coordinates. Simultaneously, since the propriety of the article is judged, it is scarcely affected by the influence of disturbance, and the malfunction of an article and noise can be discriminated, so that no misjudgment occurs. Since the curve is divided in the X- and Y-axis directions in 512 to take out the data, it makes it possible to improve the reliability of the inspection.