An electrode assembly for measuring bio-signals includes a body, a fastening member extending from the body and provided on one side of the body, the fastening member including a spring groove formed therein and an aperture penetrating therethrough, and a spring inserted into the spring groove. The aperture receives a fastening stud of a patch which is supplied from outside. The spring compresses the fastening stud received in the aperture such that the fastening member fixes the fastening stud thereto.