Steam reforming catalyst composition and steam reforming catalyst

The purpose of the present invention is to provide a novel steam reforming catalyst composition in which catalyst performance does not decrease even in reforming reactions and reduction treatments at temperatures of 500 °C or more. Provided is a steam reforming catalyst composition comprising catalytically active particles that contain: a steam reforming catalytically active component that has the effect of promoting the steam reforming reaction; and vanadium. Adding vanadium makes it possible to minimize sintering during a reforming reaction or a reduction treatment at temperatures of 500 °C or more and thereby minimize the deterioration of catalyst performance without decreasing the original catalyst performance of the steam reforming catalytically active component.