A fired precast block prevents itself from dropping off early due to corrosion and increases service life of a blast furnace runner, etc. when used in a very vulnerable portion of the blast furnace runner, etc., and can be produced at low costs. The fired precast block has an upper surface to contact molten metal or slag, a lower surface opposing the upper surface, and a plurality of side surface. The fired precast block is used by being embedded in a castable in such a manner that the upper surface is exposed from the castable and the lower surface and the plurality of side surfaces contact the castable. Each side surface of at least one opposing pair of side surfaces includes a planar portion and an uneven portion. The uneven portion has at least one groove-shaped concave portion.