A sheet feeder includes a sheet loading tray, an air blower, a side air blower, and processing circuitry. The sheet loading tray loads sheets. The air blower blows air to the sheets to float and separate the sheets. The side air blower blows air to the sheets to separate the sheets. The processing circuitry controls a tray elevator to rise the sheet loading tray to move the sheets to an upper limit position, after a predetermined time has elapsed from a time when the sheets are loaded on the sheet loading tray. The processing circuitry causes the air blower and the side air blower to blow air to the sheets to perform sheet separation and controls the tray elevator to lower the sheet loading tray to a position at which an intermediate remaining-sheet sensor is disposed, after the sheet separation ends.