Abstract: A fluid leakage detection system includes: multiple sensors, provided in a building such as a plant, that respectively detect values of detection target amounts at the installation positions of the sensors; and a fluid leakage detection device that detects leakage of a fluid in the building based on the values of detection target amounts detected by the multiple sensors. The fluid leakage detection device includes: an actual measured value acquirer that acquires the values of detection target amounts detected by the multiple sensors; and a leakage state judgement unit that judges a leakage state of the fluid in the building based on distributions of the values of detection target amounts acquired by the actual measured value acquirer.