To provide a clean oven capable of producing the clean high-temperature atmosphere of a temperature higher than a conventional one without causing the unevenness in temperature and the thermal stress.

This clean oven comprises a heater 7, a blower 6 and a filter 8, and the air from an oven inner case 4 is heated by the heater 7 and circulated into the oven inner case 4 by the blower 6 through the filter 8. A metallic filter 8 made out of a heat resisting metal is used as the filter 8. Preferably, the metallic filter is composed of a filter element obtained by sintering a heat-resisting metallic fiber and a filter frame made out of the metal same as the metallic fiber and surrounding the element. As the metallic filter 8 has high heat-resisting temperature, high-temperature atmosphere near the heat-resisting temperature can be produced, the unevenness in temperature and the thermal stress can not be found, as it is unnecessary to cool the air at an upstream side of the filter and to reheat the air at a downstream side, and the durability of the oven can be improved.