A toner supply device for supplying toner to a developing device includes: a first toner supply portion for supplying toner to a developing hopper; a second toner supply portion for supplying the stored toner to the first toner supply portion; a first toner supply driver for driving the first toner supply portion; a first residual toner quantity detector for detecting the residual toner quantity in the first toner supply portion; a second toner supply driver for driving the second toner supply portion; a second residual toner quantity detector for detecting the residual toner quantity in the second toner supply portion; and a controller for controlling the drives of the first and second toner supply drivers by switching on and off the drives of the first and second toner supply drivers in accordance with the residual toner quantities detected by the first and second residual toner quantity detectors.