Deterioration of an O ring due to radiation heating in a vacuum heating apparatus is prevented to allow heat treatment of a substrate with good annealing properties. The vacuum heating apparatus 1 includes a vacuum chamber 2 constituted by flanges 11 and 12 having an opening portion 9 and joined together, a turbo molecular pump 17 for exhausting gas from the vacuum chamber 2, and a heater base 3 for heating a substrate 5 placed in the vacuum chamber 2. Joint surfaces of the flanges 11 and 12 are sealed by an O ring 10. Further, bonding steps 13 are formed between the heater base 3 and the O ring 10 on the joint surfaces of the flanges 11 and 12, thereby preventing thermo-radiation from the heater base 3 from reaching the O ring 10 through the joint surfaces of the flanges 11 and 12.