The invention aims at providing a platinum black material, without using an expensive and rare material, which is excellent in CO poisoning inhibiting effect, H2S poisoning inhibiting effect, SO4 poisoning inhibiting effect and HCHO poisoning inhibiting effect, and a method for fluorinating platinum black. The platinum black material is characterized by fluorine adsorbed on its surface. The method for fluorinating platinum black is characterized by allowing platinum black to stand in a mixed gas atmosphere of n inert gas and fluorine in a low-pressure chamber to make fluorine adsorbed on the surface of the platinum black.