The influence of deagglomeration on an agglomerated sample, the dispersion media for a non-oxide sample, and the measuring conditions for a mixed sample on the particle size distribution are investigated in the present paper. It is found that deagglomeration is effective for dispersing an agglomerated powder well, regardless of the type and output power of the ultrasonic disrupters used. Ethanol is a useful dispersion medium for achieving stable measurements of non-oxide samples. In the measurement of a mixed sample, the measured distributions by Xray sedimentation do not coincide with the distribution calculated from the weight ratio for each original sample. However, they coincide with the modified distribution from the X-ray absorption ratio for each original sample, because the cumulative mass % in this measuring principle is determined on the basis of the relationship between the X-ray transmittance ratio and the suspension concentration, depending on the sample materials.