Summar yIn preparation for the leakage of chemical substances from factories and business establishments caused by disasters and accidents, it is desirable for each local government to grasp the daily stock amount of chemical substances in advance. This time, the technique to estimate the stock amount of chemical substances in factories and business establishments from PRTR notification data was examined.Using existing survey data by the Ministry of the Environment, the relationship between the annual handling amount of chemical substances in factories and business establishments and the stock amount on the first day of the fiscal year and the end of the fiscal year was analyzed, and it was found that the stock amount was about . to .of the handling amount (about weeks to days). We have developed a method to estimate the handling amount from the release and transfer amount of PRTR notification data, and it seems that the estimation of the stock amount becomes possible by combining with this technique.