Abstract: The present invention provides a Ni-based alloy, a heat-resistant and corrosion-resistant component, and a heat treatment furnace component, all of which have excellent corrosion resistance and mechanical strength at high temperatures. The Ni-based alloy of the present invention consists of, by mass %, Al: more than 5.0% and up to 26.0%, and Zr: more than 0% and up to 5.0%, the balance being Ni and unavoidable impurities. The Ni-based alloy preferably contains more than 0% and up to 5.0% of B, by mass %, in a combined amount with Zr. Moreover, it is preferable that the Ni-based alloy has P value and Q value and satisfies a relationship of Q value ? 0.89 × P value - 0.53, when the P value is obtained from a formula -18.95 + 0.1956 × Ni% + 0.1977 × Al% + 0.2886 × Zr% + 12.4 × B%, and the Q value is obtained by dividing an area percentage of Ni3Al precipitated on the surface of the alloy by 100.