A Hall thickness detection device for a sheet-like medium, comprising: a mounting frame, a reference shaft which has two ends mounted to the mounting frame via bearings, and a floating roller assembly, wherein the mounting frame is configured to mount and carry the reference shaft and floating roller assembly; wherein the floating roller assembly comprises: a holder, at least one floating roller, wherein one end of the holder is fixedly mounted with respect to the mounting frame through a floating roller rotating shaft, and another end of the holder is rotationally assembled to the floating roller to form a free end, a torsion spring, which is provided between the floating roller rotating shaft and the holder to allow the floating roller to elastically press against the reference shaft, a detection block, which is fixedly mounted to a side, facing away from the floating roller of the holder; and a sensor, which is opposed to the detection block and fixedly mounted with respect to the mounting frame for detecting displacement of the detection block in a non-contact manner, wherein a connection line between an axial center of the floating roller and an axial center of the reference shaft is in line with a detection center of the detection block and a detection center of the sensor, an elastically pressing point of the floating roller pressing against the reference shaft forms a tangent point, a distance from an axial center of the floating roller rotating shaft to the tangent point is equal to a distance from the axial center of the floating roller rotating shaft to a detection center of a surface of the detection block, and a connection line from the tangent point to the axial center of the floating roller rotating shaft is at an angle of 45 degrees with respect to a direction of a conveying path of the sheet-like medium. a mounting frame, a reference shaft which has two ends mounted to the mounting frame via bearings, and a floating roller assembly, wherein the mounting frame is configured to mount and carry the reference shaft and floating roller assembly; wherein the floating roller assembly comprises: a holder, at least one floating roller, wherein one end of the holder is fixedly mounted with respect to the mounting frame through a floating roller rotating shaft, and another end of the holder is rotationally assembled to the floating roller to form a free end, a torsion spring, which is provided between the floating roller rotating shaft and the holder to allow the floating roller to elastically press against the reference shaft, a detection block, which is fixedly mounted to a side, facing away from the floating roller of the holder; and a sensor, which is opposed to the detection block and fixedly mounted with respect to the mounting frame for detecting displacement of the detection block in a non-contact manner, a holder, at least one floating roller, wherein one end of the holder is fixedly mounted with respect to the mounting frame through a floating roller rotating shaft, and another end of the holder is rotationally assembled to the floating roller to form a free end, a torsion spring, which is provided between the floating roller rotating shaft and the holder to allow the floating roller to elastically press against the reference shaft, a detection block, which is fixedly mounted to a side, facing away from the floating roller of the holder; and a sensor, which is opposed to the detection block and fixedly mounted with respect to the mounting frame for detecting displacement of the detection block in a non-contact manner, wherein a connection line between an axial center of the floating roller and an axial center of the reference shaft is in line with a detection center of the detection block and a detection center of the sensor, an elastically pressing point of the floating roller pressing against the reference shaft forms a tangent point, a distance from an axial center of the floating roller rotating shaft to the tangent point is equal to a distance from the axial center of the floating roller rotating shaft to a detection center of a surface of the detection block, and a connection line from the tangent point to the axial center of the floating roller rotating shaft is at an angle of 45 degrees with respect to a direction of a conveying path of the sheet-like medium.