A nacelle cooling system of a wind turbine has cooling blocks which are arranged in order to respectively surround one or more heating devices installed inside a nacelle, a passage pipe line which is connected to the cooling blocks for coolant to flow, a primary heat exchanger which is connected to the passage pipe line and arranged on the outer lateral surface of the nacelle so as to seal the nacelle from outside, and a secondary heat exchanger which is capable of discharging heat generated inside the nacelle into outside the nacelle and constructed to seal the nacelle from outside.