A disassembly apparatus of a power generator installed in a nacelle has an I-shaped beam, a pressing plate, anchor bolts, a trolley and a chain block. The I-shaped beam extends horizontally above the frame of the power generator. The pressing plate is disposed on the I-shaped beam. The anchor bolts extend along both sides of the I-shaped beam to pierce the pressing plate and are screwed into threaded holes extending downward of the frame. The trolley is provided movably to roll on the upper surface of the lower flange. The chain block is hung from the trolley. The flange removed from the frame is hung and moved vertically by the chain block, and is moved horizontally by the trolley.