PURPOSE: To accurately measure a polished degree of cereal grains, especially rice grains, irrespective of two rice-polishing systems of a grinding and a friction system, by a method wherein a reflectiopn light measuring device and a transmission light measuring device and a transmission light measuring device are connected to a polished degree gauge through an arithmetic unit.

CONSTITUTION: A sample tray 11 is placed below an integration ball 10 whose inner surface forms mirror. A light source 7, a shutter 8, a heat ray absorbing filter 15, a monochromatic light filter 9, a light-collecting lens 9 are located above the ball 10. Plished rice grains are placed in the tray 11, and through the projection of a light from the light source 7, a reflection light from a sample rice grain is amplified through a light-receiving element 13. Meanwhile, the transmission light passed through the sample rice grains is collected by a light-receiving element 13', and the signal is connected to an amplifier 5'. A black box 12 is placed around the tray 11, and only the transmission light is perceived by the element 13'. Signals from the amplifiers 5 and 5' are connected to an operating element 4, and further are connected to a digital indicator 1 for polished degree. Additionally, a digital indicator 3 for reflection degree, a digital indicator 2 for transmission degree, and a constant- voltage device 6 are installed. The above system enables the accurate measurement of both two polished degrees of rice grains, polished under a friction system, which have a smooth surface and a better transparent feeling, and of rice grains, hulles under a grinding system, which have a coarse surface.