A multi-feed detection device including: an arm member (14 to 17) supported swingably and configured to come into contact with a traveling sheet; and detecting means (25 to 27) for detecting whether a plurality of the traveling sheets are overlapped and fed, on the basis of swing of the arm member (14 to 17), wherein the detecting means (25 to 27) includes a target and non-contact measuring means for measuring, in a non-contact manner, a positional relation between the non-contact measuring means and the target, the positional relation being changed by swing of the arm member (14 to 17), characterized in that the multi-feed detection device further comprises: a bracket member (12, 13, 28) swingably supporting the arm member (14 to 17); a turnable support shaft supporting the bracket member (12, 13, 28) and configured to turn the bracket member (12, 13, 28); and a holder member (13, 21 to 24, 28) rotatably attached to the support shaft and fixedly supported so as not to be turned by turn of the support shaft, and in that the target of the detecting means (25 to 27) is provided to one of the arm member (14 to 17) and the holder member (13, 21 to 24, 28), the non-contact measuring means of the detecting means (25 to 27) is provided to the other of the arm member (14 to 17) and the holder member (13, 21 to 24, 28), and the support shaft is configured to be turned in such a way as to move the arm member (14 to 17) between an operation position at which the arm member (14 to 17) comes into contact with the sheet and a retreat position at which the arm member (14 to 17) is separated from the sheet. an arm member (14 to 17) supported swingably and configured to come into contact with a traveling sheet; and detecting means (25 to 27) for detecting whether a plurality of the traveling sheets are overlapped and fed, on the basis of swing of the arm member (14 to 17), wherein the detecting means (25 to 27) includes a target and non-contact measuring means for measuring, in a non-contact manner, a positional relation between the non-contact measuring means and the target, the positional relation being changed by swing of the arm member (14 to 17), characterized in that the multi-feed detection device further comprises: a bracket member (12, 13, 28) swingably supporting the arm member (14 to 17); a turnable support shaft supporting the bracket member (12, 13, 28) and configured to turn the bracket member (12, 13, 28); and a holder member (13, 21 to 24, 28) rotatably attached to the support shaft and fixedly supported so as not to be turned by turn of the support shaft, a bracket member (12, 13, 28) swingably supporting the arm member (14 to 17); a turnable support shaft supporting the bracket member (12, 13, 28) and configured to turn the bracket member (12, 13, 28); and a holder member (13, 21 to 24, 28) rotatably attached to the support shaft and fixedly supported so as not to be turned by turn of the support shaft, and in that the target of the detecting means (25 to 27) is provided to one of the arm member (14 to 17) and the holder member (13, 21 to 24, 28), the non-contact measuring means of the detecting means (25 to 27) is provided to the other of the arm member (14 to 17) and the holder member (13, 21 to 24, 28), and the support shaft is configured to be turned in such a way as to move the arm member (14 to 17) between an operation position at which the arm member (14 to 17) comes into contact with the sheet and a retreat position at which the arm member (14 to 17) is separated from the sheet.