An oxide film is formed on a substrate by performing a cycle a predetermined number of times. The cycle includes: continuously performing supplying in advance an oxidant to a substrate in a process chamber and simultaneously supplying the oxidant and a precursor to the substrate in the process chamber, without having to purge an interior of the process chamber between the act of supplying in advance the oxidant and the act of simultaneously supplying the oxidant and the precursor; stopping the supply of the oxidant and the precursor to the substrate in the process chamber and purging the interior of the process chamber; and supplying the oxidant to the substrate in the purged process chamber.