PROBLEM TO BE SOLVED: To provide a sterilization device and a sterilization method that facilitate management.SOLUTION: The sterilization device includes: a gas supply device 12 which supplies hydrogen peroxide gas into a sealed space 100 a detector 13 which can detect concentration of the hydrogen peroxide gas in the sealed space 100 and humidity in the sealed space 100 storage means 41 of storing a threshold with which prescribed sterilization effects in the sealed space 100 are obtained and control means 14 of calculating a first integrated value of variation in concentration of the hydrogen peroxide gas supplied into the sealed space 100 with an elapsed time and a second integrated value of variation in humidity in the sealed space 100 with the elapsed time, comparing the product of the calculated first integrated value and the second integrated value with the threshold, and determining that the prescribed sterilization effects are obtained in the sealed space 100 when the product of the first integrated value and the second integrated value is equal to or larger than the threshold.
