To provide a heat treatment method for giving efficient and economical heat treatment to a number of wafers with high quality, and to provide its vertical or horizontal device suitable for the heat treatment method.

The individual wafers 2 are supported on a boat 3 in a vertically rising manner. The boat 3 on which the number of wafers 2 are aligned and supported in the vertically rising manner is arranged in a core pipe 11 of the vertical heat treatment device 1 in the horizontal direction and a material gas flow path 6 easy to pass therethrough is formed between the adjacent wafers 2, 2 in the vertical condition. Material gas is fed into the core pipe 11 in the vertical direction and the fed gas is put in contact with each wafer 2 in the vertical condition through the gas flow path 6 to form a uniform film thickness on the surface of the wafer.