To provide a metal matrix composite body showing a low thermal expansion coefficient which matches that of AlN and Si by forming a reinforcing material from a recrystallized silicon carbide.

As the reinforcing material for a metal matrix composite body, a recrystallized silicon carbide (RSiC) of 5-40 vol.% porosity (2-30 vol.% is preferred) is used. The original material of the RSiC is SiC powder having 2-mode particle distribution, and one side is a particle 20 of relatively large particle size (about 100 μm) while the other side is a particle 21 of very small particle size which reaches micron range (particle size <1 μm), with the small particle 21 made to be confine in the gusset of the large particle 20. Then it is sintered at 2,200°C or higher in an inert gas atmosphere. Thus, it is manufactured with no contraction, without tightening of pores among large particles. With the use of different porosity, a thermal expansion coefficient is also adjusted very accurately.