The telescope of the University of Tokyo Atacama Observatory has a primary mirror with a diameter in 6.5m. In order to fabricate the reflecting film initially on the mirror surface and to maintain its optical performance over a long period, we have a mirror-coating facility being installed at the summit of Co. Chajnantor (5,640m). The facility consists of a clean booth for stripping off the old film, a mirror coating chamber, and a cart with a lifter for handling the primary mirror. A conventional evaporation system with a metal pre-wetted filament array is adopted for achieving various optical requests. Among the many development items, the fabrication of the transportation and lifting cart has been already completed. It has efficient performance in load capacity (>60 tons) and maximum lifting height (1,750 mm). A cleaning machine having injection nozzles that can realize an efficient and safe cleaning sequence also been completed. A test of the evaporation system using dedicated filaments and filament boxes, which are customized to the TAO's requirements, has shown a uniform coating on a test mirror. An array pattern of the filaments has also been decided based on the coating tests to satisfy the optical specification of the telescope. A detailed design of the main chamber has been almost completed, it is only waiting for the production in the near future.