Document feeder and image capturing device preventing empty stamping associated with improper positioning of printing unit. Document feeder A, conveying document originals from a document placement location, along a predetermined conveyance path (12), and to a document information-capturing location (5, 6), is furnished with: a printing unit (8), which is shiftable along the document widthwise direction approximately orthogonal to the document conveyance direction, and is for carrying out predetermined printing onto conveyed documents; and a detection unit (S4), provided in the conveyance path further upstream in the conveyance direction than the printer unit (8), that detects whether a conveyed document will pass inside the limits of the range in which the printer unit (8) prints.