An image forming device is provided which includes a developer carrying body and a developer supply device to supply a developer to the developer carrying body. The developer supply device includes a plurality of transfer electrodes, and a transfer voltage applying unit to apply traveling-wave shaped transfer voltages to the plurality of transfer electrodes. The developer includes a fine particle charged in a predetermined polarity and a fine particle charged in a polarity opposite to the predetermined polarity. The transfer voltage applying unit is configured to apply the transfer voltages having waveforms, which make a fly height of the fine particle charged in the predetermined polarity higher than a fly height of the fine particle charged in the opposite polarity, to the plurality of transfer electrodes.