PROBLEM TO BE SOLVED: To provide a translucent ZrOsintered body excellent in light transmissivity, strength, water resistance, and thermal degradation resistance.SOLUTION: A ZrOsintered body containing 4.5-6 mol% of YOis composed of a tetragonal crystal of an axial length ratio c/a of a unit lattice of 1.013-1.017, a tetragonal crystal prime of 1.004-1.009, and a cubic crystal and has an average particle diameter of &le；1 &mu；m and a light transmissivity (600 nm, 1.0 mm thickness) of &ge；30%. The sintered body is produced by heating a compact of ZrOpowder that contains 4.5-6 mol% of YOsolid solute in ZrOand has a BET of 6-20 m/g and a mean particle diameter of &le；0.7 &mu；m, to 1,380-1,420°C at a rate of 400°C/h or more and keeping the temperature for 0.5-2 minutes, and then cooling to 1,230-1,350°C at a rate of 400°C/h or more and keeping the temperature for a predetermined period.
