Benign metastasizing leiomyoma (BML) is a rare condition that affects other organs out of the uterus. Recently, a few case reports in which 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) has been used to distinguish the malignancy have been published. Here, the authors present a case of BML with metabolic activity on PET, in which needle biopsy of the uterus was efficient to make diagnosis.