A sheet medium processing device, comprising a stacking mechanism, a first switching mechanism and a retractable paper baffle adjacent to the medium exit of the stacking mechanism, which are mounted on a frame, the stacking mechanism comprising a lower ticket stacking assembly, an upper ticket stacking assembly capable of moving parallelly above the lower ticket stacking assembly and a parallel movement confining mechanism configured to limit the moving trajectory of the upper ticket stacking assembly, the upper ticket stacking assembly and the lower ticket stacking assembly respectively comprising a bracket, a belt, and at least two belt pulleys mounted on the bracket to support the belt, wherein a passage for transporting mediums or a space for stacking mediums is formed between the belt of the upper ticket stacking assembly and the belt of the lower ticket stacking assembly; the upper ticket stacking assembly has a tendency of moving towards the lower ticket stacking assembly by gravity, wherein the first switching mechanism simultaneously controls the reciprocation of the paper baffle and the parallel movement of the upper ticket stacking assembly, enabling the stacking mechanism to be selectively in a transport state and a stacking state, the first switching mechanism comprising: a push plate hinged on the frame by a hinge shaft to rotate around the hinge shaft, and having an initial position and a lifting position; a cam, provided below the push plate and configured to rotate the push plate from the initial position to the lifting position; a third elastic element, configured to have the push plate being in a tendency of maintaining at the initial position, wherein the push plate has a second edge abutted against the periphery of the cam and a third edge for pushing the upper ticket stacking assembly away from the lower ticket stacking assembly when the push plate is at the lifting position, characterized by a swinging bracket comprising a left side wall and a right side wall which are pivoted on the frame, and a connection wall extended transversely between the left side wall and the right side wall, wherein the paper baffle is provided on the connection wall; and a second elastic element configured to have the paper baffle on the swinging bracket being in a tendency of stretching out, wherein the push plate further has a first edge pushing the paper baffle on the swinging bracket to retract when the push plate is at the initial position. a push plate hinged on the frame by a hinge shaft to rotate around the hinge shaft, and having an initial position and a lifting position; a cam, provided below the push plate and configured to rotate the push plate from the initial position to the lifting position; a third elastic element, configured to have the push plate being in a tendency of maintaining at the initial position, wherein the push plate has a second edge abutted against the periphery of the cam and a third edge for pushing the upper ticket stacking assembly away from the lower ticket stacking assembly when the push plate is at the lifting position, characterized by a swinging bracket comprising a left side wall and a right side wall which are pivoted on the frame, and a connection wall extended transversely between the left side wall and the right side wall, wherein the paper baffle is provided on the connection wall; and a second elastic element configured to have the paper baffle on the swinging bracket being in a tendency of stretching out, wherein the push plate further has a first edge pushing the paper baffle on the swinging bracket to retract when the push plate is at the initial position.