A method of measuring a relative phase of a bio-cell using a digital image sensor, comprising the steps of firstly filtering a light emitted from a light source, using a first polarizer and a first wave plate, which are arranged in order in a optical path, exposing a bio-cell to the firstly filtered light, secondly filtering the light passing through the bio-cell, using a second wave plate and a second polarizer, which are arranged in order in the optical path, and sensing an intensity of the secondly filtered light, by each of pixels of the image sensor, wherein, as conditions of the second filtering are varied, optical properties of the bio-cell are calculated using the intensity of the light in a pixel-wise manner.