The compressive strength of a boron carbide sintered compact is improved by controlling crystals of the boron carbide to a polycrystalline structure having a grain size distribution in which coarse crystals with a grain size of 20 .mu.m or more and fine crystals with a grain size of 10 .mu.m or less are mixed in an appropriate ratio. Furthermore, a protective member having an improved compressive strength can be provided using the boron carbide sintered compact having a polycrystalline structure in which coarse crystals and fine crystals are mixed in an appropriate ratio or a boron carbide sintered compact containing graphite and silicon carbide.