Provided is a method of manufacturing a semiconductor device using a substrate processing apparatus including a reaction chamber in which a plurality of substrates are stacked at a predetermined distance; a first gas supply nozzle installed to extend to a region in which the plurality of substrates are stacked; a second gas supply nozzle installed to extend to a different position from a position at which the first gas supply nozzle is installed in the region in which the plurality of substrates are stacked; a first branch nozzle installed at the first gas supply nozzle in a direction parallel to major surfaces of the plurality of substrates, at least one line of which is branched in a direction of the second gas supply nozzle, and including at least one first gas supply port; and a second branch nozzle installed at the second gas supply nozzle in the direction parallel to the major surfaces of the plurality of substrates, at least one line of which is branched in a direction of the first gas supply nozzle, and including at least one second gas supply port; wherein the first gas supply port and the second gas supply port are installed adjacent to each other in a direction that the plurality of substrates are stacked, the method including the steps of: loading the plurality of substrates into the reaction chamber; and forming SiC films by supplying at least a silicon-containing gas and a chlorine-containing gas or a silicon/chlorine-containing gas through the first gas supply port and supplying at least a carbon-containing gas and a reduction gas through the second gas supply port.