A heat treatment system may include: a heat treatment furnace; a return line; and a processor. The return line may include: a first processing line; a second processing line; an entrance line connected to the first processing line and the second processing line and located upstream of the first processing line and the second processing line on the return line; and an exit line connected to the first processing line and the second processing line and located downstream of the first processing line and the second processing line on the return line. The processor may include: a configured to process the saggar on the first processing line; and a configured to process the saggar on the second processing line.