PROBLEM TO BE SOLVED: To provide a food machine capable of sterilizing both inside of a treatment tank and a decompression system without pressure-proofing the treatment tank for sterilization, and to guarantee sterilization of the decompression system even under the control based on the temperature or pressure inside the treatment tank.SOLUTION: A valve 26 is mounted in an exhaust pathway 7 from within the treatment tank 2 by a decompression means 5. After reducing the pressure within the treatment tank 2 by the decompression means 5, steam is fed into the treatment tank 2 via an exhaust pathway 7 from a sterilization steam feeding pathway 60 while the valve 26 is closed, and the pressure within the treatment tank 2 is recovered to the extent not to exceed the atmospheric pressure. Inside of the treatment tank 2 and the area from the treatment tank 2 to the valve 26 are sterilized by keeping the inside of the treatment tank 2 at set temperature or at least at set pressure for at least a set period of time.
