Leiomyoma of the ovary is relatively rare and its origin is still controversial. Here, we report 2 cases of ovarian leiomyoma. Case 1, a 59-year-old woman who complained of abdominal distention. Ultrasonography and computed tomography revealed a large solid mass in the lower abdomen. The mass was diagnosed as uterine myoma preoperatively, but it turned out to be a left ovarian tumor at laparotomy. The tumor was about an adult-head size, grayish, elastic hard, and solid. In case 2, a fist-sized mass was accidentally detected in the right ovary of a 84-year-old woman during laparotomy for rectal cancer. Histologically both tumors were composed of solid proliferation of short spindle-shaped cells, that formed interlacing fascicles and showed varying degrees of hyalinization. Both tumors were diagnosed as leiomyoma. Although this tumor is rather infrequent, it is necessary to consider leiomyoma for differential diagnosis, when a solid tumor is detected in the ovary.