PURPOSE: To surely measure concentration of π water which is a dilute solution in simple means usefully to agriculture and marine industries by culturing bacteria using π water and examining size and shape of colony.

CONSTITUTION: Bacteria are cultured in a culture medium using π water and concentration of π water is measured by size and shape of colony changed by proliferation of the bacteria. Furthermore, when measured, a measuring apparatus composed of Schale 1 for putting the culture medium therein, cover 2 for covering the upper part in a closed state, microfilter 4 for closing opening 3 provided on the nearly top and part 8 for placing bacteria grains installed in the lower part of the microfilter 4 is preferably used.