An apparatus for pre-activation of a polymer electrolyte fuel cell includes a first plate and a second plate hot pressing the unit cell stack, each having a flow channel supplying water vapor to opposing inner surfaces with the unit cell stack therebetween and including a resistor producing heat, a compressor, a temperature controller and a water vapor supplier connected to the flow channels of the plates. The apparatus for pre-activating a polymer electrolyte fuel cell may be used to prepare a prep-activated integrated body of a polymer electrolyte fuel cell membrane electrode assembly and gas diffusion layers by performing hot pressing while supplying water vapor to the unit cell stack to hydrate the polymer electrolyte membrane. And the apparatus for pre-activating a polymer electrolyte fuel cell is used to monitor physical damage of the membrane electrode assembly based on the change of degree of vacuum at a fuel electrode side and an air electrode side using, thereby detecting the leaking membrane electrode assembly in advance.