A portable medical device has a medical measuring apparatus and an elastic mounting portion. The medical measuring apparatus has a body. The body has a mounting mechanism. The elastic mounting portion is arched, adapted to be mounted around a subject's wrist or arm and has two edges and an attaching mechanism. The two edges are opposite to each other and define a gap for placement of the subject's wrist or arm. The attaching mechanism detachably engages the mounting mechanism of the body of the medical measuring apparatus. Thus the portable medical device is convenient for daily use and for carrying on a subject by simply mounting around the subject's wrist or arm by the elastic mounting portion.