An ion supply device includes an ion generator for generating ions for removing static electricity, a carrier gas supply unit for supplying to the ion generator a carrier gas for carrying the ions generated in the ion generator, and an ion supply nozzle for blowing the ions and the carrier gas from the ion generator through a blow-off opening toward an electricity removal target from which static electricity is to be removed. A slit is provided at the blow-off opening and has an increased width as the slit gets distant from the electricity removal target. The ion supply nozzle includes an internal flow path and a plurality of internal fins provided at a portion of the internal flow path near the blow-off opening so that the ions and the carrier gas blown from the slit is uniformly distributed along a lengthwise direction of the slit.