PURPOSE: To dispense with visual checking and to eliminate the generation of an inferior product due to the exhaustion of an adhesive, by detecting the residual amount of an adhesive by confirming that a prescribed amount of the adhesive has been applied to a printed circuit board after the adhesive had been applied.

CONSTITUTION: After the coating work of an adhesive, an NC apparatus 6 judges whether final coating has been applied to one printed circuit board 5 and, if it is not judged as the final one, the next coating is continued. If final coating has been applied, a detection timing signal is generated from the NC apparatus 6 and the amount of the coated adhesive on the board 5 is judged by an optical fiber photoelectric sensor 7 and, if said amount is a prescribed one, it is judged that the coating of the board 5 with the adhesive was completed and the next coating work of the board is performed. If not the prescribed amount, the exhaustion of the adhesive is judged to stop operation and the adhesive is replenished by an operator and the succeeding coating of the adhesive is continued.