An apparatus for depositing a thin film on a substrate by chemical vapor deposition (CVD) includes a material container for containing a liquid CVD source material; a material feeder for feeding the liquid CVD source material from the material container to a vaporizer while keeping the CVD source material liquid; a vaporizer for vaporizing the liquid CVD source material fed from the material feeder by heating the liquid CVD source material to a high temperature to form a CVD source material gas; a reaction chamber connected to the vaporizer by a pipe for forming a thin film on a substrate using the CVD source material gas; and a thermostatic box surrounding the reaction chamber, wherein both of the vaporizer and piping connecting the vaporizer to the reaction chamber are located within the thermostatic box.