IMAGE FORMING APPARATUS AND TONER CONCENTRATION CONTROL METHOD

PROBLEM TO BE SOLVED: To properly control a toner image density without using a density sensor.SOLUTION: In an image forming apparatus, a storage device 45 stores calibration data 51 showing a correspondence relation between a plurality of image density setting values and a dot counted value with a predetermined toner consumption amount. And, an image density setting part 65 derives an estimate value of a toner image density from a dot counted value counted in a period in which toner is consumed in a predetermined toner consumption amount on the basis of the calibration data 51 and determines and updates the image density setting values based on the derived estimate value. In particular, the image density setting part 65 specifies the density adjustment tendency of a user based on the density adjustment recorded by a density adjustment recording part 66 and determines and updates the image density setting values based on the derived estimate ID value, according to the density adjustment tendency.