Abstract: Provided is a method of manufacturing a semiconductor device capable of suppressing variation in thickness of oxide films among a plurality of SiC wafers. Forming first inorganic films on lower surfaces of a plurality of SiC wafer, and then performing etching of the plurality of SiC wafers so that 750 nm or more of the first inorganic film is left in thickness, and then forming oxide films on upper surfaces of the plurality of SiC wafers by performing thermal oxidation treatment in a state in which a first SiC wafer of the plurality of SiC wafers is placed directly below any one of at least one wafer, including at least one of a dummy wafer and a monitor wafer, and a second SiC wafer of the plurality of SiC wafers is placed directly below a third SiC wafer of the plurality of SiC wafers.