The present invention provides a heat treatment method for a silicon wafer in which, with respect to a surface of the silicon wafer made flat at an atomic level by a high-temperature heat-treatment at 1,100° C. or more, a surface roughness of the wafer can be reduced compared with the conventional one while maintaining a step terrace structure on the surface of the above-mentioned wafer, and the surface of such a wafer can be formed stably. In the heat treatment method for the silicon wafer in which the step terrace structure is formed on the surface of the silicon wafer, after the silicon wafer is heat treated at 1,100° C. or more in a heat treatment furnace in a reducing gas or inert gas atmosphere, the atmosphere in the furnace is arranged to be of argon gas at a temperature of 500° C. or more in the furnace when reducing the temperature and argon gas continues to be introduced into the furnace until the silicon wafer is removed from the furnace, so that the step terrace structure on the surface of the above-mentioned silicon wafer may be maintained and a root mean square roughness Rms per 3 μm×3 μm may be 0.06 nm or less.