To provide an alloy for a fuel cell stack joining bolt jointly having high temperature strength and creep fracture ductility remarkably superior to those of SUS304 in spite of its thermal expansion coefficient close to that of ferritic heat resistant steel particularly at high temperature exceeding 700°C.

The alloy for a fuel cell stack joining bolt is composed of an Ni based superalloy having a composition comprising, by mass, 0.005 to 0.15% C, ≤0.5% Si, ≤0.5% Mn, 15 to 24% Cr, one or two kinds selected from Mo and W so as to satisfy Mo+W/2:5 to 17%, 0.5 to 2.0% Al, 1.3 to 2.5% Ti, ≤5% Fe and one or two kinds selected from 0.002 to 0.02% B and 0.01 to 0.2% Zr, and the balance substantially Ni of 48 to 78%. The alloy preferably comprises 0.5 to 1.4% Al, 1.3 to 1.8% Ti and ≤1% Fe, and the balance substantially Ni of 50 to 75%.

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