The object of the present invention is to provide a catalyst that is highly active and capable of maintaining its activity for a long period of time even in a high-temperature environment. The present invention is a catalyst including: a porous carrier which is comprised of one kind of or two or more kinds of metal oxides; and catalyst particles which are comprised of precious metals or precious metal oxides and supported on the above porous carrier, characterized in that the catalyst particles include: clustered particles formed by the aggregation of first precious metal atoms; and second precious metal ions bound to the above clustered particles. Preferably, the first precious metal and the second precious metal are different metal species which are selected from the group consisting of platinum, palladium, rhodium, ruthenium, silver, gold, iridium and osmium.