The invention relates to a human body lower limb automatic measuring device and a human body lower limb automatic measuring method. The device comprises an image collecting device and an image processor, wherein the image collecting device comprises a pair of special measuring trousers and a measuring work table, the front side and the left side of the measuring work table are respectively provided with a camera machine case, the camera machine case is connected with the measuring work table through a metal rod, a camera and a flash lamp are arranged on the camera machine case, the image processor consists of a computer host machine and a display, and the image collecting device and the image processor are connected through a USB (universal serial bus) data wire. The device and the method provided by the invention have the beneficial effects that a front side image and a lateral side image are collected through a camera, the automatic measurement on the lower limb dimension of the human bodies is realized, all dimensions required by the medical compression stockings can be simply, fast and accurately obtained, the defects of time waste, labor waste and the like the manual measurement in the prior art are avoided, the device and the method can also be used for realizing the application to other leg dimension requiring occasions, the cost is low, and the operation is simple and convenient.