Provided is a stacking mechanism that includes a paper feed tray including a paper inlet through which a recording medium to undergo a recording process is to be supplied; a paper output tray on which the recording medium that has undergone the recording process and been transported is to be stacked, the paper output tray being superposed on the paper feed tray; a pivotal shaft that allows the paper output tray to pivot with respect to the paper feed tray so as to expose the paper inlet of the paper feed tray; and a lock mechanism that locks the paper output tray displaced about the pivotal shaft, at a predetermined position.