PURPOSE: To enhance etching accuracy by setting a light receiving device for receiving light transmitted through a photomask at a position away from the loci of an etching solution sprayed and detecting the etching end point according to the output of the light receiving device.

CONSTITUTION: A photomask is placed on a supported rotary stand, and control section 14 is actuated to spray an etching solution from fan-shaped spray nozzle 4 as well as to rotate the stand. Light receiving device 6 is set which receives light transmitted through the mask at a position away from the loci of the solution sprayed. The output of light receiving device 6 is amplified 8 and converted into digital signals with A/D converter 9. Operation circuit 10 takes the difference between the former signal and the latter one to average the difference with a plurality of continuous dots. This output is converted into a binary code at a predetermined level, the time at which the binary code signal changes from 1 to 0 is considered as the etching end point, and the signal is sent to section 14. When section 14 receives the signal, it stops pressurizing pump 17 to stop spray of the etching solution from nozzle 4, and water is sprayed upon the mask from nozzle 22.