A ceramic sintered body includes tungsten carbide, zirconia, and alumina. The content of the tungsten carbide is 20 to 50 vol %, and the content of the zirconia is 5 to 25 vol %. The crystal phase of the zirconia is a tetragonal crystal or a mixture of tetragonal and monoclinic crystals. The ceramic sintered body does not substantially include Ti compounds. The average particle diameter of the tungsten carbide, the average particle diameter of the zirconia, and the average particle diameter of the alumina are all 1 μm or less.