The invention has an object of providing catalysts that are not corroded in acidic electrolytes or at high potential, have excellent durability and show high oxygen reducing ability. An aspect of the invention is directed to a process wherein metal carbonitride mixture particles or metal oxycarbonitride mixture particles are produced from an organometallic compound of a Group IV or V transition metal, a metal salt of a Group IV or V transition metal, or a mixture of these compounds using laser light as a light source.