To provide a yttria sintered body having an excellent corrosion resistance to halogen-based corrosive gases and plasma and an excellent thermal shock resistance, and adapted for use as a component member in manufacturing apparatuses for semiconductor and liquid crystal devices, particularly in a plasma process apparatus. A yttria sintered body including tungsten of an average particle size of 3 μm or less dispersed in the yttria so that a ratio of the tungsten relative to the yttria is ranging from 1 to 50% in terms of weight, and having an open pore rate of 0.2% or less and a thermal shock resistance by water submersion method of 200° C. or larger.