A sheet feeder comprising: a cassette; a feed roller; a sloping separation plate provided on a downstream side of the cassette in a sheet feeding direction; and a separation member that includes a first separation claw and second separation claw, the first separation claw being closer a bottom surface of the cassette than the second separation claw, the separation member and the feed roller cooperating with each other to separate and feed the sheets, sheet by sheet; wherein the sloping separation plate has openings so as to allow distal projecting portions of the first separation claw and second separation claw to project through the sloping separation plate, respectively, and wherein, a first angle formed between the distal projecting portion of the first separation claw and the sloping separation plate is larger than a second angle formed between the distal projecting portion of the second separation claw and the sloping separation plate.