PURPOSE: To continuously measure coat thickness when coating and to control coat thickness easily and exactly, by computing it from irradiation of high frequency waves and measurement of reflected waves.

CONSTITUTION: A coat thickness meter consisting of an oscillator 4, receiver 6, computer 7, converter 8, display device 9, etc. is attached to a coater 1. It computes the thickness wet coat 5 through emitted high frequency waves and received reflected waves, converts it in accordance with an angle of the coater 1, the kind of coating material, components of its volatile metter, etc., and displays its dry coat thickness on the device 9, thus permitting easy and exact control of coat thickness to be executed by this method of coating and simultaneous measuring coat thickness.