A fluid leakage detection system has a detection space to which working oil leaked out through a rod seal is guided; the rod seal being configured to seal an annular gap between a piston rod and a cylinder head; a sensor unit configured to detect pressure in the detection space; and a controller configured to acquire detected result from the sensor unit, wherein the controller has: a calculation unit configured to calculate a pressure parameter representing a pressure fluctuation in the detection space; a determination unit configured to determine occurrence of leakage of the working oil based on the pressure parameter; and the pressure parameter includes an upper limit value and a lower limit value of the pressure fluctuation obtained from the detected result detected by the sensor unit within a predetermined detection period.