NOVELTY - Growing a composite metal sulfide thin film involves immersing first carrier for photochemical deposition and second carrier for chemical bath deposition in a reaction tub filled with an alkaline solution comprising metal ion and thiosulfate/thiourea; and irradiating first carrier with light source producing light, such that the metal sulfide thin film is grown by photochemical deposition and chemical bath deposition on the first and second carriers.    USE - For growing a composite metal sulfide thin film (claimed) used for creating a better amenity environment and to decompose odors, bacteria and stains during the process of sterilization, oxidative decomposition, and deodorization; for forming solar cell panels, photocatalyst thin films, photoreactors and optoelectronic substrate.    ADVANTAGE - Both photochemical deposition and chemical bath deposition can occur simultaneously in the reaction tub. Therefore, the metal sulfide thin film or composite metal sulfide thin film is grown on the first and second carriers with a shorter deposition time. Since thiosulfate in the solution is used for generating electrons and sulfur atoms in the photochemical deposition process and forming metal complexes in the chemical bath deposition process, a smaller amount of electroplating solution is used on both deposition processes and the efficiency for forming the metal sulfide photocatalyst is significantly improved. The method and apparatus are provided for forming a large-area metal sulfide thin film.    DETAILED DESCRIPTION - Growing a composite metal sulfide thin film involves immersing a first carrier for photochemical deposition and a second carrier for chemical bath deposition in a reaction tub filled with an alkaline solution comprising at least a metal ion and a sulfur-based compound, where the second carrier is arranged vertical to a bottom surface of the reaction tub; and irradiating the first carrier with a light source producing light, such that the metal sulfide thin film is grown by photochemical deposition and chemical bath deposition on the first and second carriers; and where the sulfur-based compound comprises thiosulfate (S2O32-) and thiourea (CSN2H4).