To provide a method for effectively classifying granular substances having different specific gravities.

A container 1 with a plurality of riffles 2 formed on the bottom face so as to leave a space between them, is arranged on a slant so that the riffles 2 extend in obliquely downward directions. A liquid mixed with powder granularity materials having different specific gravities is fed into the container 1 from the upper inclined part 7. Horizontal periodical vibration is applied to the container 1 by a vibrator 5, and at the same time, nonlinear vertical vibration having a difference in acceleration in the vertical direction is applied to it by a vibrator 6. The powder granularity materials are classified and discharged from 8-9 of the container 1 based on differences in their specific gravities.