A high definition multimedia interface (HDMI) mortise adapter includes two sets of terminals arranged in radiant and cluster blocks, a first case, a second case, separator, and a plastic member; cluster blocks and terminals being thermoset and incorporated with each other by stubs and blind holes to allow comfortable placement of the separator in between; both cases being locked to each other by means of plate disposed on the inner side and perforated frame; and retainer and inclined angular plate disposed on the side board of the first case in conjunction with the plastic member secure both sets of terminals between both cases.