A sheet-feeding apparatus includes a passage, a sheet-feeding roller disposed at an entrance of the passage, and a paper pressing mechanism including a paper pressing device and a driving mechanism. The driving mechanism drives the paper pressing device to move towards and away from the sheet-feeding roller. The driving mechanism includes a power source, a rotating shaft connected to the power source, and an arm attached to the rotating shaft. As the rotating shaft rotates in a first direction, the arm actuates the paper pressing device to move away from the sheet-feeding roller. As the rotating shaft rotates in a second direction, the arm releases the paper pressing device, so the paper pressing device moves towards the sheet-feeding roller and presses a paper sheet upon the sheet-feeding roller.