An object of the present invention is to provide a catalyst in which a reaction initiation temperature at which self-heating function is exhibited is low and which is capable of suppressing carbon accumulation even when a reaction is repeated. The catalyst of the present invention is a catalyst including a CeZr-based oxide, silicon, and a catalytically active metal, wherein the CeZr-based oxide satisfies Ce x Zr y O 2 (x + y = 1) and the silicon satisfies molar ratios of 0.02 ‰¤ Si/Zr and 0.01 < Si/(Ce + Zr + Si) < 0.2. When the catalyst is used, a reduction temperature for generating initial oxygen deficiency can be decreased. Depending on the catalytically active metal, a reduction activation treatment can be performed even at about 20°C without any need for heating. In a repeated hydrogen generating reaction, the deposition of carbon generated on the surface of the catalyst can be suppressed, and a decrease in catalytic activity can be prevented. Therefore, the catalytic performance can be maintained
