PURPOSE: To accurately expose radiation to a lesion by accurate estimating a position and size of the lesion even in the case the lesion in the internal organs moves by the respiration of a subject.

CONSTITUTION: The device is provided with a first means for obtaining a target image from plural scanogram images photographed at the time of exhaust of respiration, a second means for deriving a target image A in the radiation exposing direction in order to expose radiation by computing the interporation based on each target image obtained by a first means, a third means for obtaining the target image from plural scanogram images photographed at the time of intake of respiration, a fourth means for deriving a target image B in the radiation exposing direction in order to expose by computing the interporation based on each target image obtained by a third means, a fifth means for estimating a position of the target image extending from the time of exhaust to the time of intake of respiration by computing the interporation based on the target image A and the target image B, and a sixth means for exposing radiation to a position of the target image estimated by a fifth means.