The image forming apparatus includes a developing device that holds a two-component developer to develop an image, a detecting unit that outputs a reference output value and a second output value when the two-component developer is stirred and carried at a stirring/carrying speed corresponding to a second image forming mode, a stirring/carrying member that stirs and carries the two-component developer, and a controlling unit that controls the toner concentration based on the reference output value when forming an image in a first image forming mode, and controls the toner concentration, when forming an image in the second image forming mode, a corrected output value obtained by correcting an output value in the second image forming mode with a difference value between the reference output value and the second output value.