A carbon/silicon composite material wherein a silicon carbide containing carbon layer which is formed by silicon and boron carbide being penetrated from a surface of a carbon substrate into the inside thereof to allow the silicon and carbon of the carbon substrate to react with each other so as to be converted into silicon carbide and in which the silicon carbide is dispersed generally uniformly along a depth direction is formed on the carbon substrate as a first layer, the silicon carbide containing carbon layer having a thickness of not less than 1 mm.