An image forming device includes: a transfer unit transferring a toner image to a sheet; a resistance measurement member disposed on the upstream side in a sheet carriage direction of the transfer unit and for measuring resistance of the sheet; a charge elimination member disposed between the transfer unit and the resistance measurement member in the sheet carriage direction; a first voltage applying unit applying voltage for resistance measurement to the resistance measurement member; and a second voltage applying unit applying voltage of reverse bias of the voltage for resistance measurement to the charge elimination member. The width of a charge elimination region by the charge elimination member is wider than that of a charged region by the resistance measurement member in a direction perpendicular to the sheet carriage direction. The absolute value of the voltage for charge elimination is smaller than that of the voltage for resistance measurement.