Disclosed is a silicon carbide type diffusion tube comprising a diffusion tube base made of reaction-sintered silicon carbide having an iron concentration of 20 ppm or below and a density of 3.0 g/cm<3> or over, and a silicon carbide layer consisting of a high-purity silicon carbide film having an iron concentration of 5 ppm or below deposited on the inner surface of the tube base and a silicon carbide type diffusion tube comprising a diffusion tube base made of reaction-sintered silicon carbide, and a silicon carbide layer consisting of a Si-depleted layer formed in the inner wall of the reaction-sintered silicon carbide tube base and a high-purity silicon carbide film deposited on the Si-depleted layer, said silicon carbide film having a thickness of more than 0.5 mm.
