The invention relates to an organic Rankine cycle power generation device which comprises a pre-heater, a falling film evaporator, a gas-liquid separator, an expansion machine, a power generator, a heat regenerator, a condenser, a liquid storage device and a working medium pump; the falling film evaporator comprises a heat source fluid inlet, a heat source fluid outlet, an organic working medium inlet, an organic working medium outlet, a three-stage uniform liquid separation component with a spray device, a tube bundle I, a liquid collecting and separating device, a tube bundle II, an organicworking medium steam loop, a shell and the like. The organic Rankine cycle power generation device provided by the invention has the benefits that with the adoption of the pre-heater and the falling film evaporator, the evaporation temperature is increased so as to be closer to the temperature of a heat source fluid; compared with the prior art, as the falling film evaporator adopts film evaporation heat transfer, the evaporation temperature of an organic working medium can be effectively increased by about 2 DEG C; under the condition that the condensation temperature is constant, the theoretical ORC efficiency can be improved by more than 2 percent, and the power generation quantity of the device is improved by about 2 percent; and in addition, the system design can also be optimized.