Sheet feeder and image forming apparatus

A sheet feeder comprising:

• a sheet stacking tray provided to stack a sheet to be supplied to a main body, the sheet stacking tray being configured to be opened and closed with respect to the main body by rotation about a rotation axis defined in a direction perpendicular to a sheet feeding direction;
• a first width regulating member provided in the sheet stacking tray and configured to regulate a side edge of the sheet in a sheet width direction and to have a variable regulating width;
• an auxiliary tray provided at a position in the main body where the auxiliary tray does not move in association with an opening/closing operation of the sheet stacking tray, the auxiliary tray being configured to stack the sheet in cooperation with the sheet stacking tray;
• a second width regulating member provided in the auxiliary tray and configured to regulate the side edge of the sheet in the sheet width direction and to have a variable regulating width;
• a link member interlocking the first width regulating member and the second width regulating member in a regulating width changing operation;
• and
• a sheet feeding member provided in the main body and configured to feed one by one the sheets stacked over the sheet stacking tray and the auxiliary tray.