An exhaust gas heat exchanger having stacked flat tubes includes a stacked tube body configured by stacking a plurality of flat tubes in multiple tiers with spaces therebetween and arranged inside a case; exhaust gas flows in from a first end part of the stacked tube body in a tube axis direction, circulates through each flat tube, and flows out from the a second end part; and cooling water from the case is supplied to the first end part to circulate along an exterior surface side of each flat tube. The cooling water is introduced into the tubes from two locations of the case and in mutually opposite directions which are parallel to flat surfaces of the tubes and vertical in the axis direction of the flat tubes.