A device for identifying thickness of a sheet-like medium, comprising a frame, comprising two lateral plates (41, 42) and a facade, configured to carry a thickness shaft, a floating shaft and a sensor; wherein: both ends of the thickness shaft are arranged on the two lateral plates (41, 42) of the frame via bearings; both ends of the floating shaft are arranged on the two lateral plates (41, 42) of the frame via bearings and an outer surface of the floating shaft is tangently contacted with an outer surface of the thickness shaft; and the sensor is arranged on the facade of the frame, and configured to detect an amplitude of a point of tangency where the floating shaft is tangent to the thickness shaft; wherein one end of the thickness shaft is fixedly connected with a first synchronous pulley, the first synchronous pulley is connected with a first synchronous pulley gear via a first synchronous belt; one end of the floating shaft is fixedly connected with a second synchronous pulley, the second synchronous pulley is connected with a second synchronous pulley gear via a second synchronous belt; the first synchronous pulley gear meshes with the second synchronous pulley gear and is assembled on a shaft of a driving motor, wherein the second synchronous pulley gear sleeves on a bearing, the bearing sleeves on a shaft which is riveted with the lateral plate of the frame, and the second synchronous pulley gear is rotatable with the shaft, wherein the first synchronous pulley gear comprises a synchronous pulley part and a gear part, and the first synchronous belt sleeves on the first synchronous pulley and the synchronous pulley part of the first synchronous pulley gear; wherein the second synchronous pulley gear comprises a synchronous pulley part and a gear part, the second synchronous belt sleeves on the second synchronous pulley and the synchronous pulley part of the second synchronous pulley gear, and the gear part of the second synchronous pulley gear meshes with the gear part of the first synchronous pulley gear. both ends of the thickness shaft are arranged on the two lateral plates (41, 42) of the frame via bearings; both ends of the floating shaft are arranged on the two lateral plates (41, 42) of the frame via bearings and an outer surface of the floating shaft is tangently contacted with an outer surface of the thickness shaft; and the sensor is arranged on the facade of the frame, and configured to detect an amplitude of a point of tangency where the floating shaft is tangent to the thickness shaft; wherein one end of the thickness shaft is fixedly connected with a first synchronous pulley, the first synchronous pulley is connected with a first synchronous pulley gear via a first synchronous belt; one end of the floating shaft is fixedly connected with a second synchronous pulley, the second synchronous pulley is connected with a second synchronous pulley gear via a second synchronous belt; the first synchronous pulley gear meshes with the second synchronous pulley gear and is assembled on a shaft of a driving motor, wherein the second synchronous pulley gear sleeves on a bearing, the bearing sleeves on a shaft which is riveted with the lateral plate of the frame, and the second synchronous pulley gear is rotatable with the shaft, wherein the first synchronous pulley gear comprises a synchronous pulley part and a gear part, and the first synchronous belt sleeves on the first synchronous pulley and the synchronous pulley part of the first synchronous pulley gear; wherein the second synchronous pulley gear comprises a synchronous pulley part and a gear part, the second synchronous belt sleeves on the second synchronous pulley and the synchronous pulley part of the second synchronous pulley gear, and the gear part of the second synchronous pulley gear meshes with the gear part of the first synchronous pulley gear.