To estimate the internal dose of a Chinese visiting scholar internally contaminated because of the Chernobyl Accident, the contents of ¹³⁴Cs and ¹³⁷Cs in urine were measured using a Ge(Li) γ-spectrometer. The internal doses were calculated based on data from the ICRP Publications. The effective doses from ¹³⁴Cs and ¹³⁷Cs were estimated to be 61μSv and 98μSv, respectively. The sum of 159μSv was lower than the total effective dose (310μSv), from the inhalation and ingestion of natural radionuclides. The dose of ¹³¹I was also reviewed referring to the UNSCEAR 2000 Report. The equivalent effective dose of ¹³¹I was estimated to be 2.9mSv, 18 times more than the amount of ¹³⁴Cs and ¹³⁷Cs. Therefore, it is considered that the earlier estimation of internal doses of ¹³¹I is important in evaluating radiation injuries from a nuclear reactor accident.