According to one embodiment, an image forming apparatus includes: a light source unit including light emitting elements for red, green, and blue; an image pickup section configured to receive, from a reference board on which light from the light source unit is irradiated, reflected light to pick up an image of the reference board; and a control section configured to control the light emitting elements of the light source unit to separately emit light, acquire separate data picked up by the image pickup section, select data having a smallest luminance value among the separate data, and control light amounts of all the light emitting elements of the light source unit with the selected data set as a reference.