PURPOSE: To perform accurate operation to detect sheets in a double feed state by a method wherein a means to exert a carrying load on a sheet is formed with a roller, and the roller is supported through a support frame rocked around a position not coinciding with the rotation center of the roller.

CONSTITUTION: A means arranged facing a carrying means and exerting a carrying load on a sheet is provided. By applying resistance on a carrying sheet, a sheet to which a double feed occurs is forced to be displaced, and a double feed is detected by a sheet sensor arranged to a sheet carrier passage. In this case, a means to apply resistance on the sheet is formed with a roller 15, and the roller 15 is supported through a support frame rocked around a position 11 not coinciding with the rotation center of the roller 15. This constitution causes upper and lower sheets, to which a double feed occurs, to be displaced from each other in the middle of carriage by means of the roller 15, and performs an accurate operation to detect sheets in a double feed state.