An oxygen concentration is lowered in accordance with a set lowering process, and thereafter a heat treatment is performed. Accordingly, the heat treatment is performed to a substrate W while the oxygen concentration in a heat treating space HS is lowered. Consequently, a treatment atmosphere within the heat treating space is able to be made suitable for a heat treatment process, leading to appropriate film deposition. In addition, the oxygen concentration is lowered in accordance with a concentration level in recipes. This avoids an excessively lowered oxygen concentration, leading to prevention of reduced throughput.