A sheet feeder includes: a cassette main body; a side cursor; and a restriction part. The cassette main body houses a sheet to be fed in a predetermined sheet feeding direction. The side cursor is installed onto the cassette main body to be slidable in a sheet width direction perpendicular to the sheet feeding direction, and positions the sheet in the cassette main body. The restriction part increases sliding load of the side cursor with respect to the cassette main body when the side cursor slides and passes a standard size point that is a stopping position on the cassette main body when a sheet of a standard size is positioned.