Provided is a heat exchanger capable of ensuring both heat exchange performance and reliability against corrosion. The heat exchanger includes a plurality of fins each having a flat plate shape, openings provided in each of the plurality of fins, and cylindrical parts arranged on outer peripheries of the openings, each having an inner diameter larger than an outer diameter of each of the openings. The plurality of fins are stacked on one another with the cylindrical parts interposed between the plurality of fins. The openings and the cylindrical parts are configured to form a liquid passage pipe, and the openings protrude further inside than are the cylindrical parts.