The invention relates to a height adjusting device and a displaying device that adopts the height adjusting device. The height adjusting device comprises a base, an elastic element, a locking unit and a supporting frame with a containing space, wherein, the locking unit comprises two sliding blocks, and the supporting frame comprises two friction railways that are obliquely arranged; wherein, thesupporting frame is arranged on the base, the elastic element and the locking unit are contained in the containing space, one end of the elastic element supports the locking unit, the other end of the elastic element is connected with the base, two sliding blocks of the locking unit are correspondingly contained in the two friction railways of the supporting frame, and one of the two sliding blocks is butt-connected with the inner surface of one of the friction railways. By combining the friction railways with the locking unit, the displaying device can effectively lock a displaying panel at a certain height, thus the whole displaying device has simple structure and high reliability.