A sheet feeder, which is included in an image forming apparatus, includes a sheet feeding unit to feed a sheet, a sheet separating unit disposed opposite the sheet feeding unit to separate the sheet together with the sheet feeding unit, a bottom plate on which the sheet is loaded, a pressing unit having a leading end and movably disposed between the bottom plate and the sheet separating unit, and a support to rotatably support the pressing unit such that the leading end of the pressing unit contacts and separates from the sheet feeding unit.