Sliding member, manufacturing method thereof, mechanical seal ring using sliding member and mechanical seal using mechanical seal ring

A sliding member having a sliding surface comprising a silicon carbide sintered body having a primary phase comprising mainly silicon carbide, and a subphase having a different composition from the primary phase and containing at least boron, silicon and carbon. The ratio of pores having a roundness of 6 μm or less and a pore diameter of 10 to 60 μm with respect to all pores having a pore diameter of 10 μm or more in the sliding surface is 60% or more. This enables retention of good seal properties even in a long-term continuous use. The subphase in the silicon carbide sintered body is preferably granular crystal phases dotted among a plurality of the primary phases. This provides excellent lubricating liquid holding performance as well as excellent thermal conductivity and excellent thermal shock resistance properties.