A heat exchanger for common use for both a boiler and a hot water supply is provided, which includes a plurality of inner plate members (110) having inner plate member grooves formed on either side of the upper end thereof, and a burner provided on the bottom surface thereof, to thereby perform a combustion chamber function; combustion heat fin tubes (120) formed of a number of heat exchange tubes on the outer circumferential surface of which transfer heat fins are formed; an insulation member (130) which is installed in an identical area along the inner walls of the inner plate members; and an independent heat exchanger body which is connected with the combustion heat fin tubes. Thus, a heat exchanger for a condensing or noncondensing gas boiler can be manufactured at low cost, through the common heat exchanger Further, two kinds of heat exchangers can be manufactured through a single common heat exchanger to thereby make an additional process unnecessary.