||This is the experimental study on airtightness measurements of 40 testers in order to identify the uncertainty of data by testers in the airtightness measurement of buildings. It is not easy to identify exact airtightness because airtightness contains a lot of uncertainty etc. by measurement methods, measurement conditions, testers. Therefore, we compared testers' airtightness measurement results by carrying out education of the same contents during the same period and using the same environmental conditions and equipment. We reviewed uncertainty about the result of airtightness by comparing and analyzing airtightness data of the same building measured by testers. According to analysis results, uncertainty by testers was found to be lower than other uncertainty factors. Through uncertainty analysis research, when measuring airtightness, the main error cause and degree of uncertainty by testers can be easily identified and can be usefully utilized in improving measured experimental values.