A sheet feeder includes a housing having a cassette housing part recessed horizontally from the front surface toward the depth direction and a sheet feed cassette that can be drawn from the cassette housing part. The sheet feed cassette has an open top for storing sheets of paper. The sheet feeder includes a pressure plate provided pivotably about a first pivot so as to be inclined downwardly toward the depth direction of the sheet feed cassette and a pressure mechanism that presses sheets of paper against a pick-up roller when the sheet feed cassette is pushed into the cassette housing part. The sheet feeder includes a pressure plate regulation mechanism that inclines the pressure plate downwardly toward the depth direction while separating sheets of paper on the pressure plate or the pressure plate from the pick-up roller when the sheet feed cassette is drawn from the cassette housing part.