The present invention provides an image forming apparatus that adjusts the amount of light of a light-emitting unit with high accuracy and suppresses an increase in control time that is required to adjust the amount of light, a scanning optical apparatus, and control methods thereof. To accomplish this, the image forming apparatus of the present invention derives a threshold current and a bias current of the light-emitting unit. Further, the image forming apparatus of the present invention supplies the bias current to the light-emitting unit when causing the light-emitting unit to emit light in an amount of light corresponding to the minimum density level, and supplies a current that is larger than the threshold current to the light-emitting unit when causing the light-emitting unit to emit light in an amount of light corresponding to a density level that is larger than that minimum density level.