A case of 68-year-old woman. The patient was scheduled for laparoscopic transverse colectomy, due to early colorectal cancer diagnosis. Right after the surgery began, electrocardiogram showed a R-on-T phenomenon premature ventricular contraction leading to ventricular tachycardia and ventricular fibrillation. Although chest compression and electric defibrillation made the rate come back to sinus rhythm, we used emergency coronary angiography after halting the surgery since an elevation in ST segment had been confirmed in precordial leads on 12-lead electrocardiogram. As there was complete occlusion in left anterior descending coronary artery (LAD), the patient appeared to have a high-grade stenosis before surgery. Placing a stent on LAD, we carried out laparoscopic transverse colostomy once again at a later date. In this case, given that the coronary artery had had a high-grade stenosis before the surgery, it is highly likely that some kind of disruption in the myocardial oxygen balance caused myocardial ischemia, but that was difficult to predict by preoperative assessment. However, we successfully resuscitated the patient through swift and proper treatments and the case successful ended up being radical operation without any after effects thanks to a proper judgment made by cooperation between surgeons and internal cardiologists. (195 words)