A chemical vapor deposition unit is invented for forming a uniform thin film over the entire surface of a substrat by the vapor-deposition. The chemical vapor deposition unit comprises a reaction chamber isolated from the outside and kept under vacuum, a susceptor, on which at least one substrate is placed, installed in the reaction chamber such that it can rotate, and an injector, including independently formed first and second gas passages, and first and second gas injecting pipes that communicate with the respective gas passages and respective outlets, for injecting respective first and second gases onto the susceptor, the injector injecting the different gases independently. The injector further comprises a gas injecting part for communicating with the second gas passage so that only the second gas, which is a non-reactive carrier gas, is injected in a central region of the susceptor.