THERMAL TREATMENT APPARATUS

Provided is a heat treatment device capable of performing a heat treatment process for multiple large area substrates while preventing damage to a process tube due to the weight of a boat on which the large area substrates are loaded. The heat treatment device according to the present invention comprises: a process tube which has the frontside and backside formed therein to be opened and provides heat treatment space; a process chamber to surround the process tube; a heater module to supply heat to the process tube; a front door module which is installed on the frontside of the process tube to form a boat gate to allow a boat on which multiple substrates are loaded to access to the heat treatment space; a back door module which is installed on the backside of the process tube to seal or close the backside of the process tube; and a boat support unit which is installed in the frontside door module and the backside door module to cross the heat treatment space of the process tube without being in contact with an inner wall of the process tube and supports the boat.