Particle reinforcement via the insertion of hard particles is a promising process in materials reinforcing. Particle-reinforced spheroidal graphite martensitic cast iron (SGMC), in which mixed particles of cermet and cemented carbide are dispersed, was achieved by an insertion process. A four-point bending strength test was applied to evaluate the particle composite material. An evaporative pattern process was used on the bending-test specimen to form a composite layer in the central part. Using a combination of three sizes of cermet particles and two sizes of cemented-carbide particles, the bending strength was found to increase with each small-particle combination. The Weibull coefficient m of the four-point bending strength of the particle-reinforced composite material (PRCM) ranged from 4 to 13, and m was large in the specimen with large bending strength.