Useful material for making low-dose radiographing and an increase in the image quality compatible with each other is provided. An image analysis unit of a central server derives the granularity of a region of interest by analyzing an X-ray image transmitted from a client terminal. A storage processing unit stores the granularity, the X-ray image, and radiographing information in a storage device so as to be associated with each other. A search processing unit searches for the radiographing information, which is matched with search conditions designated from the client terminal, and granularity, which is associated with the radiographing information, from the storage device. A statistical data generation unit generates a scatter plot, which has granularity on the vertical axis and a radiation dose on the horizontal axis, as statistical data. The statistical data is transmitted to the client terminal and is displayed on a display of the client terminal.