There is provided a fluid detection device that detects a flow velocity or a flow rate of a fluid flowing through a piping, the fluid detection device including: a sound detection unit that detects a sound from the piping, and outputs a frequency signal; a signal processing unit that calculates a strength ratio of the frequency signal on the basis of the frequency signal and a predetermined reference frequency signal; and a data conversion unit that obtains the flow velocity or the flow rate on the basis of the strength ratio of the frequency signal and a predetermined fluid characteristic function.