After carrying an LCD substrate in a reaction container of a heat treatment unit, blowing a previously heated helium gas from a gas supply part, which opposes to the surface of the LCD substrate, over the entire surface of the LCD substrate. The temperature of the LCD substrate is raised by radiation heat of a heater and heat exchange with the helium gas. After performing CVD or annealing in the reaction container, cooling the LCD substrate by blowing a gas for heat exchange having a temperature about a room temperature from the gas supply part over the entire surface of the LCD substrate. Return the cooled LCD substrate to a carrier in the carrier chamber via a conveyance chamber.