A thermal analysis apparatus possesses has a cylindrical furnace tube axially inserted in a cylindrical heating furnace, and a pair of sample holders extending axially inside the furnace tube. The furnace tube is supported by two axially spaced groups of butting members, each group having three or more butting members that are disposed in circumferentially spaced-apart relationship on the outside of the furnace tube and that butt against the furnace tube to restrain positional deviation thereof in a radial direction while permitting expansion and contraction thereof in the axial direction during heating of the furnace tube by the heating furnace.