PURPOSE: To automate the inspection of the appearance quality of a cloth and to enrich the content of the appearance inspection thereby to enhance the quality of the inspection, by analyzing the frequency of image signals obtained from an inspecting cloth and studying the spatial frequency.

CONSTITUTION: The reflecting light from a transferred cloth is photographed by a line sensor camera 20 to obtain video signals. The obtained video signals are sent to a shading correcting circuit, 60 for the purpose of shading correction. The video signals after the correction are developed to a two-dimensional image of one screen by a line sensor camera interface 61. The video signals of one screen are Fourier-transformed by a two-dimensional Fourier transforming device 71, and then converted to a power spectral value by a power spectrum converter 72. The value is processed through the common logarithmic operation to change the scale by a Log converter 73. The areal average value of the power spectrum of each frequency band is obtained by an areal average value circuit 74 with the use of divided areas corresponding to preset frequency bands. A classifying/rating circuit 80 outputs signals of the inspecting result of the appearance quality corresponding to the power spectrum.