To provide a new method for biostimulation in groundwater pollution.

A method for purification of groundwater pollution using anaerobic microorganisms having a pollution-purifying capacity comprises the addition of a chemical for the anaerobic microorganisms, and monitoring of items including total organic carbon (TOC), pH, dissolved oxygen (DO), and oxidation-reduction potential (ORP) of groundwater. It is preferable that adding requirements of the chemical are set by using these monitoring results and a groundwater quality change cycle model together.