a sheet supply device includes a sheet storing section on which sheets are stacked and are stored ; a sheet feed unit controlled by a controller that feeds the sheets stored in the sheet storing section to a next process ; and an air blower controlled by the controller that blows air to the sheets stored in the sheet storing section , the air blower has an air nozzle and a shutter that can adjust an area of the air nozzle , and the shutter increases or decreases the air flow rate of the air being blown to the sheets , wherein a force provided by the air blower to push up the sheets is exerted on the sheets , such that a less force is exerted when the sheets are being fed compared to when the sheets are not being fed .