To easily and correctly set an infrared ray emissivity of a glass container 1 of which a temperature is measured by thermography 24.

Hot air from a hot air supply means 12 is blown to the glass container 1 conveyed by a conveyor 2 disposed in a can body 4 to heat it, the temperature of the heated glass container 1 is measured by the thermography 24, and whether drying and sterilization are completely performed or not is determined. A temperature sensor 26 is disposed on a heating portion B provided with the heating means 12 to decide the infrared ray emissivity of the glass container 1, and the temperature sensor 26 is coated with a glass material. A temperature in a heating area 20 is measured by the temperature sensor 26, a temperature of the temperature sensor 26 coated with the glass is measured by the thermography 24, and the infrared ray emissivity of the glass container 1 is decided on the basis of a result of the measurement.