An object of the present invention is to provide a heat exchanger made of a Co-based alloy that has high heat resistance and excellent mechanical properties compared to a conventional heat exchanger that is brazed. In the heat exchanger made of a Co-based alloy according to the present invention, the Co-based alloy contains 0.08 to 0.25% by mass of C, 0.1% by mass or less of B, and 10 to 30% by mass of Cr, and contains 5% by mass of Fe. Below, Ni is included at 30% by mass or less, the total of Fe and Ni is 30% by mass or less, and W and/or Mo are included, and the total of W and Mo is 5% by mass or more and 12% by mass It is less than or equal to Ti, Zr, Nb, and Ta, and the sum of Ti, Zr, Nb, and Ta is 0.5% by mass or more and 2% by mass or less, and 0.5% by mass or less of Si, and 0.5% by mass or less. Mn and 0.003 to 0.04% by mass of N, the remainder is composed of Co and impurities, the impurities have a chemical composition containing 0.5% by mass or less of Al and 0.04% by mass or less of O, The heat exchanger is a polycrystalline material having an average crystal grain diameter of 5 μm or more and 150 μm or less of the matrix crystal, and in the crystal grains of the polycrystalline material, an MC-type carbide phase containing the Ti, the Zr, the Nb and/or the Ta It is characterized in that the particles are precipitated at an average interparticle distance of 0.13 µm or more and 2 µm or less.
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