In ductile metal particle-reinforced ceramic composites, the prevention of crack opening by the metal particles bridging the surface of the matrix crack is said to be the cause of toughening of such a composite. Since the radii of the particles in such a composite are considered to be varied, at the stage of modeling such a composite, the distribution of the radii of particles must be considered. Micromechanics is one of the powerful methods which can take the microstructure of the composite into consideration. In the present research, micromechanical analysis is performed of the metal particle-reinforced composite with crack-bridging particles of various radii, by both introducing the stereological concept to the micromechanical model and considering interfacial debonding between a particle and a matrix. The expressions of energy release rates for both a matrix crack and a debonding one, which include the terms expressed only by the probability density function of the distribution of the radii of particles, can be obtained.