To determine the clinical efficacy of application of infrared energy to the beating heart as a means of creating electrical blocks, an original infrared coagulator (KIRC-119; Phomec Inc, Tokyo, Japan) was applied to the atrium of a patient with atrial fibrillation. A postoperative electrophysiologic study was performed to confirm its efficacy. The coagulator was applied epicardially to the beating heart concomitant with an on-pump beating heart coronary artery bypass graft procedure. Sinus rhythm was restored during the operation, and the electrophysiologic study revealed that a bidirectional block had been created on the right atrial appendage. The infrared coagulator may facilitate performance of the epicardial Maze procedure on the beating heart.