Abstract: A gas nozzle according to the present disclosure includes a supply hole having a tubular shape and configured to guide a gas and an injection hole connecting to the supply hole. The gas nozzle configured to inject the gas from the injection hole is made from ceramics or single crystal including an oxide, a fluoride, or an oxyfluoride of a rare earth element or an yttrium aluminum composite oxide as a primary component. An arithmetic mean roughness Ra of an inner circumferential surface forming the supply hole is smaller on an outflow side than on an inflow side of the gas.