Provided is a re-operation preparation process of a reaction chamber in which epitaxial growth is performed on a wafer. The re-operation preparation process of the reaction chamber includes disposing a susceptor provided in the reaction chamber and on which the wafer is seated at a preset first position and setting a flow rate of a hydrogen gas introduced through a main valve so that the flow rate is greater than that of a hydrogen gas introduced through a slit valve and moving the susceptor to a preset second position and setting an amount of hydrogen gas introduced through the main valve while the susceptor is maintained at the second position so that the amount of hydrogen gas is less than that of hydrogen gas introduced through the slit valve. Thus, moisture and contaminants stagnant in a lower portion of the reaction chamber may be smoothly discharged along a flow of the hydrogen gas toward a discharge hole.