In a heat exchanger, fins are simply and accurately positioned in place and heat is efficiently exchanged without increasing manufacture cost, and the plurality of corrugated plate-like fins are disposed in the flow direction of a coolant in a housing. The heat exchanger has: connecting parts, which connect together the adjacent fins among the fins; protrusions formed on the connecting parts; and positioning holes for positioning the fins formed in the housing. The adjacent fins are disposed at predetermined intervals in the coolant flow direction with a predetermined offset amount in the direction that orthogonally intersects the coolant flow direction by fitting the protrusions in the positioning holes.