PROBLEM TO BE SOLVED: To provide a pretreatment method in an inexpensive bacterium measurement having excellent operability without requiring a bacterium grinding apparatus of exclusive use and a reagent. SOLUTION: Indicator bacteria of contamination in a food sanitation examination are ground by an alkali solution and mixed with a buffer solution. The concentration of the alkali solution is preferably 0.1-1.0 N and the treatment time with the alkali solution is preferably 5-10 minutes.