Certain embodiments provide an image forming apparatus including: a paper feed section; an image forming section; a transport mechanism; a sheet sensor which detects leading and trailing edges of the sheet; a sensor power source which supplies electric power to the sheet sensor; a detecting section which specifies the position of the sheet based on the position of the sheet sensor in a transport path and a detection output from the sheet sensor; and a driving control section which generates a timing signal indicating a first detection period when a leading edge of the sheet is detected and a timing signal indicting a second detection period when a trailing edge of the sheet is detected, turns on the sensor power source in the first detection period and the second detection period, and turns off the sensor power source in a period different from the respective detection periods.