To provide a fuel cell water leakage detecting apparatus capable of detecting the leakage of a trace amount of cooling water from a fuel-cell stack.

A trace amount of cooling water leaking from the stack 1 drops onto the bottom surface 4 of a easing 2 as water droplets 6, which are collected downwards along the inclination of the casing bottom surface 4 and detected as leaks by a moisture detector 5 provided at the lower end of the inclined surface. Upon detecting moisture, the moisture detector 5 outputs a leak detection signal via a signal line 8 to a warning device 7, which in turn blinks a warning lamp (not shown) or sounds a warning buzzer (not shown) to report the leakage to an operator.