A heat treatment apparatus with a process chamber, a tubular heater, a heat exhaust system and a cooling section. The heater surrounds an outer circumference of the process chamber. The heat exhaust system exhausts an atmosphere in a space between the heater and the process chamber. The cooling section blows a cooling fluid into the space to cool the atmosphere. The heater includes a tubular heat insulator, a heat generating resistor on an inner circumference of the heat insulator, and an outer shell provided on an outer circumference of the heat insulator. The cooling section includes at least one annular flow path between the heat insulator and the outer shell, and an outlet in the heat insulator. The outlet blows cooling fluid toward a vertical central axis of the heat insulator, or in a direction oblique to the direction toward vertical central axis of the heat insulator.