PURPOSE: To facilitate the sorting of wood, by scanning the surface of a wood chip with a scanning camera, forming red, green, and, if necessary, blue image data in accordance with the passing of the wood chip, and analyzing the histogram of frequency distribution of obtained data.

CONSTITUTION: In a sotor 10, a detecting station 21 is installed, which includes a line scanning camera 22 for forming an image of the surface of a wood chip 14. The movement and the position of the wood chip 14 moving on a conveyer 12 are detected by a sensor 24 fixed to the camera 22. A cutting-out station 26 and a sorting station 27 which are connected in series are installed below the station 21. Data from encoders 18, 18C, 18S and sensors 24, 14C, 24S which are installed on the three stations are inputted in a main computer control part. From a histogram 46, the multidistribution and the single distribution of color images are formed. The operations of cutting 39 and sorting 44 are executed on the basis of the above distributions.