A simple method for the determination of pyruvic acid was investigated. The pyruvic acid concentrations were determined by an enzymatic method using a urea tester, which was a simple apparatus for the determination of urea concentration. The color tone of pyruvic acid, which was developed by the enzymatic reaction, slightly differed from that of urea, but the pyruvic acid concentration determined by the urea tester was little affected by personal error. This method was effective for the pyruvic acid concentration between 2 to 18 ppm. This method is useful for the determination of timing of alcohol addition on sake brewing process.