Primary ovarian myxoid tumor such as myxoma, myxoid liposarcoma and myxoid leiomyosarcoma is extremely rare neoplasm. We experienced a case of unusual myxoid tumor of the ovary in a 25 year-old woman. She was admitted for an incidentally found ovarian mass during antenatal check. Radiologic studies revealed a 5.5x5 cm-sized solid mass in left ovary and she was undertaken left oophorectomy. Grossly, the round ovarian mass was measuring 8x6x5 cm, and the cut surface was predominantly solid with myxoid appearance. Microscopically, the tumor was surrounded by thick collagenous capsule and had moderate cellularity and rich vascularity. The tumor cells were stellate-shaped with abundant extracellular myxoid material without atypia. We initially thought this lesion as myxoma, but the cellularity was too high as an ordinary myxoma. Myxoid liposarcoma could also be considered as the differential diagnosis, however there was no convincing lipoblast. So, we diagnosed that tumor as myxoma with uncertain malignant potential.