Recently microwave tissue coagulation therapy (MCT) has been established as a therapeutic procedure for hepatocellular carcinoma (HCC). The route of approach to penetrate the tumor is two-fold: By the percutaneous route (PMCT) or by conventional laparotomy. PMCT has the advantage of less invasive therapy, however, it is not applicable to a tumor that cannot be detected by ultrasonography. Therefore, we tried MCT with mini-laparotomy. The patient was a 57-year old man with HCC located in the S6 subsegment. The operation was performed at the semi-right side up position, and laparotomy was done by skin incision of 12 cm in the right hypochondral area. MCT was performed about 30 times, with an output of 60 watts for 45 seconds at a time. Abdominal CT image showed a low-density area of 7 x 4 cm on the 18th postoperative day. Slight damage to the liver and no obvious complications were observed. We concluded that a much wider range-coagulation than PMCT was able to be obtained by MCT with mini-laparotomy, and postoperative quality of life was better than MCT with conventional laparotomy.