A developer supply device, comprising: a carrying substrate having electrodes arranged along a developer transport path at predetermined intervals to carry a developer through a traveling electric field, wherein the carrying substrate comprises: a rigid upper carrying substrate formed to stand to carry the developer upward; and a flexible bottom carrying substrate curved to be a semispherical shape and is configured to charge the developer by friction with the developer and to be connected with a lower end portion of the upper carrying substrate so as to form a bottom surface of a developer reservoir portion, and wherein a joint portion of the bottom carrying substrate connected to the lower end portion is overlapped with the lower end portion such that the joint portion carries the developer in a same direction as a direction in which the developer is carried by the lower end portion.