The present invention relates to a photographing device including a power transmission unit. The power transmission unit includes a frame unit which is connected to the second drive body, an adaptor unit which is connected to the frame unit and is selectively connected to the first drive body or the support body by external power, an actuating unit which operates the adaptor unit, and a power unit which transmits power to the actuating unit. According to the power transmission unit of the X-ray mammography device, since biopsy photography and tomography can be performed using only one power transmission unit, the weight and size of the rotating arm may be reduced, and the vibration and noise produced thereby may be reduced. Thanks to the simple operation mechanism of the power transmission unit, power loss may be reduced, and the durability of each component may be improved.