PROBLEM TO BE SOLVED: To provide an image forming apparatus which makes the improvement of S/N ratio and the reduction of the time required to form an image feasible. SOLUTION: The image forming apparatus includes an electromagnetic wave radiation means 405, an electromagnetic wave detection means 406, a drive means 403, a periodical signal generation means 411 for generating periodical signals 413, a memory means 416, processing means 414,415 and an image forming means 420. The drive means 403 changes periodically the relative positional relationship between an object 401 and the radiating part of the electromagnetic wave radiation means 406. The electromagnetic wave detection means 406 acquires electromagnetic waves from the object 401 as a time-series detection signal 412. The processing means 414,415 perform calculation using the time-series detection signal 412 and the periodical signals 413, and make the memory means 416 store. The image forming means 420 forms an image of the object from the information stored in the memory means 416. COPYRIGHT: (C)2009,JPO&INPIT