A mechanical seal is, at a sliding surface and at its vicinty, formed of a pore-dispersed cemented carbide, so that the lubricating characteristics can be improved and the strength maintained by strictly stipulating the magnitude, shape, and volumetric ratio of the pores, such that pores are contained in an amount of 0.5 to 20 volume %, formed in at least one shape selected from the group of a substantialy spherical shape and a substantially cylindrical shape, the pores in the substantially spherical shape having an average diameter of 3 to 20 .mu.m, the pores in the substantially cylindrical shape having an average diameter of 3 to 20 .mu.m and an average length in the range from the average diameter up to 300 .mu.m, and that the pores are prevented from linking to each other to give a length greater than 2 mm.