According to the present disclosure, there is provided a technique capable of efficiently heating a substrate with a light emitted from a lamp heater. According to one aspect of the technique of the present disclosure, there is provided a substrate processing apparatus including: a process vessel at least a part of which is made of opaque quartz; a substrate mounting table provided in the process vessel or in a processing space communicating with an inside of the process vessel; a lamp heater provided at a position facing a substrate placing surface of the substrate mounting table; and a plasma generator provided at an outer periphery of the process vessel and configured to excite a gas in the process vessel by a plasma.