A paper pick-up mechanism for a feeder includes a pick-up roller, a pick-up roller shaft, a separation roller, a transmission shaft, a gear set and a transmission gear shaft. Two one-way clutches are respectively coupled to the transmission shaft and the transmission gear shaft in parallel. When the transmission shaft is rotated in a direction opposite to a sheet-feeding direction, the gear set, through the cooperation of the two one-way clutches are used as a planetary gear set to lift up the pick-up roller.