A developer supply device, comprising a casing having: a developer reservoir at a bottom part of the casing; a developer amount adjustment chamber provided close to a side of the developer reservoir to communicate with a top portion of the developer reservoir; and a communication part through which the top portion of the developer reservoir and the developer amount adjustment chamber communicate with each other, and further comprising: a carrying substrate having electrodes arranged along a developer transport path to carry a developer through a traveling electric field, each of the electrodes having a longer side extending in a width direction of the developer reservoir, and a developer providing unit to provide the developer into the developer reservoir, and wherein the carrying substrate comprises an upper carrying substrate on an inner wall of the casing on an opposite side of the communication part to carry the developer upward.