A paper outputting mechanism includes a frame, a motor mounted to the frame, a paper supply tray assembly, a gear assembly, a paper pressing element, a blocking element and a plurality of elastic elements. A rear of the frame has a receiving room, a front of the frame has a slope connected with the receiving room. The paper supply tray assembly includes a first paper supply tray slidably mounted to the frame and a second paper supply tray placed on the first paper supply tray. A gear assembly is driven by the motor, the gear assembly drives the first and second paper supply tray to move frontward and rearward. The paper pressing element is up and down movably mounted to the frame and located over the slope. The blocking element is front and down slidably mounted to the frame and in front of the paper pressing element.