Sheet feeding device and image forming apparatus

A sheet feeding device comprising:

• a sheet stacking unit that is movable up and down, the sheet stacking unit being configured such that sheets to be fed are stacked on the sheet stacking unit;
• a long sheet stacking unit detachably mounted on the sheet stacking unit, the long sheet stacking unit being configured such that long sheets to be fed are stacked on the long sheet stacking unit;
• a first guide that is movable along a feeding direction of the sheets through a groove provided in the sheet stacking unit, the first guide being deformable into a shape that does not interfere with the long sheet stacking unit, the first guide being configured to guide a rear end portion of the sheets in the feeding direction of the sheets stacked on the sheet stacking unit;
• a first detector provided in the first guide, the first detector being configured to detect the sheets stacked on the sheet stacking unit by contacting an upper end of the sheets;
• and
• a closing unit detachably attached to the groove in the sheet stacking unit, the closing unit being configured to close the groove facing the first detector.