A sheet feeder comprising: a feed roller configured to feed a sheet along a conveyance path; a separation roller configured to form a nip with the feed roller and separate the sheet fed by the feed roller from other sheets; a first sheet detection sensor arranged on a downstream side of the conveyance path with respect to the feed roller in the conveyance path, and configured to detect that the sheet has reached; and a control unit configured to control rotation of the feed roller, wherein in a case where starting feeding of a subsequent sheet by the feed roller after reaching of a trailing edge of a preceding sheet is detected by the first sheet detection sensor, the control unit controls the feed roller to rotate at a first feeding speed, and upon determining that a leading edge of the subsequent sheet has passed through the nip, the control unit further controls the feed roller to rotate at a second feeding speed higher than the first feeding speed, characterized by a first conveyance roller located on the downstream side of the feed roller in the conveyance path and on the upstream side of the first sheet detection sensor in the conveyance path, and configured to convey the sheet; a second conveyance roller located on the downstream side of the first conveyance roller in the conveyance path and on the upstream side of the first sheet detection sensor in the conveyance path, and configured to convey the sheet; and a third sheet detection sensor located on the downstream side of the first conveyance roller in the conveyance path and on the upstream side of the second conveyance roller in the conveyance path, and configured to detect that the sheet has reached, wherein in a case where reaching of a sheet leading edge is detected by the third sheet detection sensor, the control unit stops the rotation of the feed roller. a feed roller configured to feed a sheet along a conveyance path; a separation roller configured to form a nip with the feed roller and separate the sheet fed by the feed roller from other sheets; a first sheet detection sensor arranged on a downstream side of the conveyance path with respect to the feed roller in the conveyance path, and configured to detect that the sheet has reached; and a control unit configured to control rotation of the feed roller, wherein in a case where starting feeding of a subsequent sheet by the feed roller after reaching of a trailing edge of a preceding sheet is detected by the first sheet detection sensor, the control unit controls the feed roller to rotate at a first feeding speed, and upon determining that a leading edge of the subsequent sheet has passed through the nip, the control unit further controls the feed roller to rotate at a second feeding speed higher than the first feeding speed, characterized by a first conveyance roller located on the downstream side of the feed roller in the conveyance path and on the upstream side of the first sheet detection sensor in the conveyance path, and configured to convey the sheet; a second conveyance roller located on the downstream side of the first conveyance roller in the conveyance path and on the upstream side of the first sheet detection sensor in the conveyance path, and configured to convey the sheet; and a third sheet detection sensor located on the downstream side of the first conveyance roller in the conveyance path and on the upstream side of the second conveyance roller in the conveyance path, and configured to detect that the sheet has reached, wherein in a case where reaching of a sheet leading edge is detected by the third sheet detection sensor, the control unit stops the rotation of the feed roller.