A sheet supply device including an elevation section for up and down movement of the sheet bundle accommodated on the sheet placement table, blow sections for blowing air to the upper side surface of the sheet bundle to float up the sheet from the aforementioned sheet bundle, and a non-contact sheet detection sensor for detecting the existence or nonexistence of a sheet at the predetermined position of the aforementioned sheet placement table. The elevation drive motor is controlled in such a way as to move the sheet bundle up and down, based on the frequency or ratio of the sheet existence in the detection result of the sheet detection sensor in the operation mode of the blow section.