PROBLEM TO BE SOLVED: To provide a method for producing a polyphosphoric acid that can produce a polyphosphoric acid with high efficiency by lactic acid bacteria.SOLUTION: A method for producing a polyphosphoric acid includes a step of preliminarily incubating at least one lactic bacterium selected from the group consisting of a strain belonging to Lactobacillus paracasei and a strain belonging to Lactobacillus plantarum, and bringing the lactic acid bacterium into a phosphate-starved state and a step of incubating the lactic acid bacterium in a phosphate-starved state on a high phosphate medium having a higher phosphate ion concentration than that of a medium after the preliminary incubation.
