A sheet feeding device (10) includes an air separating unit includes a floating air blowing unit (12) and a separating air blowing unit (13) that blow air to leading edges of a bundle of sheets in a paper feeding direction to float and separate upper sheets, and a side air blowing unit (14) that blows air to both side edges of the sheet bundle to separate each of the sheets in the bundle, an air suctioning unit (15) that suctions the air to suction a top sheet thus separated, a sheet feeding unit (16, 28, 29) that feeds the sheet thus suctioned and retained, and a control unit (101) that controls to blow floating air, to blow separating air, to blow side air, and to suction the air all at different operational timings.