[Problem to be Solved]A Ni-based alloy product consisting of, by mass percent, C: 0.03 to 0.10%, Si: 0.05 to 1.0%, Mn: 0.1 to 1.5%, Sol.Al: 0.0005 to 0.04%, Fe: 20 to 30%, Cr: not less than 21.0% and less than 25.0%, W: exceeding 6.0% and not more than 9.0%, Ti: 0.05 to 0.2%, Nb: 0.05 to 0.35%, and B: 0.0005 to 0.006%, the balance being Ni and impurities, the impurities being P: 0.03% or less, S: 0.01% or less, N: less than 0.010%, Mo: less than 0.5%, and Co: 0.8% or less, wherein a value of effective B (Beff) defined by the formula, Beff (%)=B−(11/14)×N+(11/48)×Ti, is 0.0050 to 0.0300%, and the rupture elongation in a tensile test at 700° C. and at a strain rate of 10−6/sec is 20% or more. This alloy may contain one or more kinds of Cu, Ta, Zr, Mg, Ca, REM, and Pd.