A method of classifying defects of an object includes irradiating multi-wavelength light onto the object, splitting light reflected from the object into light beams, each of the light beams having different wavelengths, obtaining image information of the object based on each of the light beams, forming a characteristic matrix that represent the wavelengths and the image information, and analyzing the characteristic matrix to determine types of the defects on the object. Thus, the defects may be accurately classified using a difference between reactivity of each of the defects in accordance with variations of the wavelengths and inspection conditions.