Abstract: A reactor for thin film deposition and a thin film deposition method using the reactor are provided. The reactor includes: a reactor block which receives a wafer transferred through a wafer transfer slit; a wafer block which is installed in the reactor block to receive the wafer thereon; a top plate disposed to cover the reactor block; a shower head which is mounted on the bottom of the top plate and diffuses gas toward the wafer; and an exhaust unit which exhausts the gas from the reactor block. A first supply pipeline which supplies a first reactant gas and/or an inert gas to the wafer; a second supply pipeline which supplies a second reactant gas and/or an inert gas to the wafer; and a plasma generator which generates plasma between the wafer block and shower head are included.