Composite material and heat dissipation part

A composite material comprising a metal matrix and a structure in which thermally conductive particles are dispersed inside the metal matrix, wherein:

• the metal matrix is composed of Cu, Ag, Al, Mg, or an alloy thereof;
• the thermally conductive particles include diamond or SiC;
• the thermally conductive particles are included at a volume ratio of 15% to 80%;
• and
• in a microstructure of the composite material, the thermally conductive particles include a large particle and a small particle with a particle size difference of 150 μm or greater, wherein:
• when the large particle is a first particle, and the small particle is a second particle, the distance between the center of the first particle and the center of a first particle most adjacent to the first particle or the second particle is 200 μm or greater;
• the first particle and the first particle most adjacent thereto or the second particle are not in contact with each other but have a metal matrix therebetween;
• and
• the thermal conductivity measured after heating the composite material to a temperature in Celsius lower by 20 to 30% than the melting point of the metal matrix has a thermal conductivity degradation rate of 5% or less based on the thermal conductivity thereof before the heating.