Provided is a hydraulic engine that generates power using oil pressure, the hydraulic engine including: a hydraulic power unit including a hydraulic tube comprising a hollow portion having an opened front end and being filled with a fluid, an amplitude amplification device that is disposed at the rear side of the hydraulic tube, an oscillator that is disposed at the rear side of the amplitude amplification device so as to be deformed and increases and decreases a pressure within the hydraulic tube, and an oscillator head that is attached to a front end of the oscillator.