A semiconductor film formation device has: a reaction vessel that includes a gas flow path to allow source gas to pass through and a substrate mount site provided in the gas flow path to mount a substrate; a temperature control means that is disposed opposite to the substrate mount site and close to the reaction vessel to control the internal temperature of the reaction vessel; and a thermal conductivity adjusting member that is disposed between the reaction vessel and the temperature control means. The thermal conductivity adjusting member has a section with a thermal conductivity different from the other section along the gas flow path.