Disclosed is a method of measuring a physiological parameter in a contactless manner. The method includes acquiring a plurality of image frames for a subject, acquiring a first color channel value, a second color channel value, and a third color channel value for at least one image frame included in the plurality of image frames. The method further includes calculating a first difference and a second difference on the basis of the first color channel value, the second color channel value, and the third color channel value for at least one image frame included in the plurality of image frames. The first difference represents a difference between the first color channel value and the second color channel value for the same image frame, and the second difference represents a difference between the first color channel value and the third color channel value for the same image frame.