An optical phase microscope using rotating-¼ wavelength plate with pinhole in the center position and Fourier transformed lens is provided. The optical phase microscope comprises an optical image generator that acquires images for a specimen to be observed, an object plane onto which light beams of the images acquired from the optical image generator are projected, a first transform lens that performs primary Fourier transformation on the light beams passing through the object plane, a ¼ wavelength plate with pinhole at the center position that is positioned to be spaced by a focal distance of the first transform lens from the first transform lens, a secondary transform lens that performs secondary Fourier transformation on the light beams passing through the ¼ wavelength plate, and a phase image generator including a photo detector on which the images of the light beams subjected to the secondary Fourier transformation is focused.