A jig used for heat treatment made from an SiC-coated silicon carbide material, wherein the SiC film is coated by the CVD method on a silicon carbide matrix in which silicon has been impregnated and wherein there are no pores with a diameter of 2 .mu.m or larger in the outer layer of the matrix within 200 .mu.m from the interface of the SiC film and the silicon carbide matrix when observed by a scanning electron microscope at a magnification of 400 times. The jig is manufactured by producing an SiC film on the surface of a silicon carbide matrix in which silicon has been impregnated by introducing a raw material compound for producing the SiC film and forming the SiC film at a temperature from 1000.degree. C. to 1290.degree. C. under a pressure from 500 to 760 Torr in a non-oxidative atmosphere. The jig exhibits superior resistance to high temperature heating cycles and excellent high thermal shock resistance required for heat treatment in semiconductor manufacturing.