The present invention is a method for a heat treatment of a silicon single crystal wafer in an oxidizing ambient, including: performing the heat treatment based on a condition determined by a tripartite correlation between a heat treatment temperature during the heat treatment, an oxygen concentration in the silicon single crystal wafer before the heat treatment, and a void size in the silicon single crystal wafer before the heat treatment. This provides a method for a heat treatment of a silicon single crystal wafer which can annihilate void defects or micro oxide precipitate nuclei in a silicon single crystal wafer with low cost, efficiently, and securely by a heat treatment in an oxidizing ambient.