Automatic document feeder

An automatic document feeder for feeding a paper sheet, said automatic document feeder comprising:

• an outer casing comprising a receiving member, wherein said receiving member is arranged at a terminal side of said outer casing, and comprises a first perforation and a second perforation;
• an upper cover pivotally coupled to said terminal side of said outer casing, so that said upper cover is rotatable with respect to said outer casing to be selectively opened or closed;
• a first pressing roller set disposed within said receiving member, and comprising a first rotating shaft and a first pressing roller, wherein said first rotating shaft is disposed within said receiving member, and said first pressing roller is sheathed around said first rotating shaft and partially protruded out of said first perforation, so that said first rotating roller is exposed outside said receiving member;
• and
• a separating device sheathed around said first rotating shaft and partially protruded out of said second perforation, so that said separating device is exposed outside said receiving member, wherein when said upper cover is opened, said upper cover is contacted with said separating device, so that said separating device is moved to shift said first rotating shaft.