An image forming apparatus includes an electromagnetic wave radiating portion, an electromagnetic wave detecting portion, a driving portion, a periodical signal generating portion for generating plural periodical signals, a memory portion, a processing portion, and an image forming portion. The driving portion changes the relative positional relationship between an object and the radiating portion. The detecting portion acquires transmitted or reflected wave from the object, as a time-series detection signal. The processing portion executes a process of multiplying the detection signals of the areas of the object with the periodical signals, and a process of adding the multiplied results and causing the memory portion to store the added results. The image forming portion forms an image of at least a portion of the object, based on information stored in the memory portion corresponding to the periodical signals, after the acquisition of the time-series detection signal, and the processes executed by the processing portion are repeated plural times for the areas of the object.