The invention relates to a thickness detection device bringing convenience to blockage elimination. The device comprises a fixed frame, a basic shaft, a detecting idle wheel mechanism, and a guiding plate, wherein the fixed frame is provided with a pair of installing side walls and a base plate, a groove hole is formed in the base plate, two ends of the basic shaft are installed on the pair of the installing side walls of the fixed frame through bearings, and a basic roller is fixedly connected on the basic shaft in a sleeved mode. The detecting idle wheel mechanism comprises a support, wherein an idle wheel is installed on the support through a bearing, a magnetism component is fixed on a surface, opposite to the idle wheel, on the support. The detecting idle wheel mechanism enables the idle wheel to keep close to the basic roller under the effect of an elastic mechanism. The guiding plate comprises a guiding front plate which is arranged between the basic shaft and the base plate of the fixed frame and a movable guiding rear plate which is arranged on one side, facing the guiding front plate, of the fixed frame. A through hole is formed in the guiding front plate, the basic roller contacts with the idle wheel through the through hole in a selective mode, and the guiding rear plate is arranged on the side walls through a rotary shaft in a rotating mode and keeps attaching with the base plate through a torsional spring.