PURPOSE: To obtain data with less variance in detection sensitivity with simple constitution by recording data on projection and data on the output of an X-ray source in an X-ray detection material which moves in synchronization with the rotation of an X-ray source and forming a tomographic image in accordance with the recorded data.

CONSTITUTION: An X-ray source S irradiates a fan beam-like X-ray toward object OBJ and the periphery thereof, and the data on the projection and the data on the output of the X-ray source are recorded in an X-ray detection material SP which rotates in synchronization with the source S. The material SP moves in an arrow direction at every rotation by a slight angle of the source S and records the data for each of the angles in a bar graph. The recorded data is conducted to an image reproducer (not shown), by which a tomographic image is formed. The data on the projection and the data on the output of the X-ray source are simultaneously recorded and therefore the correction of a fluctuation in the output of the X-ray source is made possible without requiring any detector for reference.