There is provided a method of manufacturing a semiconductor device, comprising forming a film on a substrate in a process chamber by performing a cycle a predetermined number of times. The cycle includes alternately performing supplying a halogen-based first process gas to the substrate in the process chamber, and supplying a non-halogen-based second process gas to the substrate in the process chamber. Further, an internal pressure of the process chamber in the act of supplying the first process gas is set to be higher than an internal pressure of the process chamber in the act of supplying the second process gas.