To provide a zirconia sintered body is capable of suppressing the low temperature degradation, and provides a composition that is a precursor for the sintering of the zirconia sintered body, and a plasticizer. In the X-ray diffraction pattern in the zirconia sintered body soseongmyeon, a tetragonal derived from the [200] the height of the peak to peak is present in the vicinity of [200] where a peak is generated in the cubic derived for the resulting position in height of the peak present in the vicinity of ratio is 0.4 or more, a depth of from soseongmyeon in the X-ray diffraction pattern at least 100㎛ region, [200] peak of the cubic derived for the height of the peak present in the vicinity where the [200] peak of a tetragonal derived from the resulting It produced a ratio of 0.3 or less of the height of the peak present in the vicinity of the location.