We measured the electrical resistivity of face-centered-cubic (fcc) structured iron hydrides at high pressures up to 65GPa and high temperatures in a laser-heated diamond anvil cell. The results indicate that the resistivity of stoichiometric fcc FeH_x (x ∼ 1.0) is smaller than that of fcc Fe at the same pressure and temperature conditions. The same behavior was also observed in fcc FeNiH_x (x ∼ 1.0). On the other hand, hydrogen-poor fcc FeH_x (x<0.77) showed a resistivity comparable to that of the fcc phase of pure iron. Therefore, we conclude that the stoichiometric fcc Fe (–Ni) hydride is more conductive than Fe (–Ni) with the same crystal symmetry, and the impurity resistivity of hydrogen in Fe is vanishingly small. Even if hydrogen is the major light element in the Earth's core, it would have little influence on the electrical and thermal conductivity of Fe–Ni alloys, and hence the thermal evolution of the core.