A hydrogen manufacturing apparatus for manufacturing hydrogen by utilizing heat generated in a nuclear plant. The apparatus has a heat exchanger or steam reformer to be brought into contact with cooling water containing tritium produced from the nuclear plant and a tritium permeation suppressing ceramic coating at least either the outer surface or the inner surface of the heat exchanger or steam reformer for suppressing permeation of tritium. Instead of coating with a tritium permeation suppressing ceramic, a structure prepared by combining at least two types of materials having different crystal structures may be used.