Provided by the present invention is an image forming apparatus wherein a signal to noise ratio is improved without reducing a video rate of a real-time moving image. The image forming apparatus comprises:a pixel 101 having an electromagnetic wave detecting element 111 configured to detect an electromagnetic wave;a switch 110 configured to read out a signal from the pixel;a signal generating unit 102 configured to generate a signal 114 having a predetermined period, wherein the pixel is connected to a transmission line 103 for supplying, to the pixel, the signal having the predetermined period, and to a scanning line 106 and 107 for reading out the signal from the pixel through the switch, and the pixel has a frequency converting element 113 configured to convert a frequency of a detection signal of the electromagnetic wave detecting element, using the signal having the predetermined period.