An image forming apparatus of the present invention includes a toner content controller configured to set the target value of a toner content sensor for determining, after a developing unit has been driven for a preselected period of time since the detection of the replacement of a toner cartridge, that a toner-end recovery operation has been completed. Subsequently, every time a preselected toner replenishing cycle is executed, the toner content controller determines whether or not the output voltage Vt of the toner content sensor has decreased below Vt10-0.1 V and determines, if the answer of this decision is positive, that a toner-end recovery operation has completed.