PURPOSE: To improve the accuracy in measurement by projecting parallel light rays on a region to be measured from a light source through an optical cable and a condenser lens, and sending a signal from a light receiving part into optoelectronic transducer means through optical cables.

CONSTITUTION: Light which is outputted from a laser diode 11 is projected on a region to be measured as parallel light rays through an optical fiber 10, an optical connector 7 and a condenser lens 5 in a light projecting part 2. The parallel light rays from the lens 5 are transduced into an electric signal in optoelectronic transducers 12 and 13 through first and second slits 3 and 4 in a light receiving part 1, an optical connector 6 and optical fibers 8 and 9. The signals from the transducers 12 and 13 are inputted in a signal processing device 14, and the amount of snowstorm is operated and measured. The result is recorded and displayed. Thus the measuring accuracy can be enhanced.