It is intended to provide an organic peracid polymer composition which is stable, odorless and has sufficient water solubility and is suitably used as a bactericide, a bleaching agent and a cleaning agent. By mixing and dissolving an organic acid polymer, hydrogen peroxide and an inorganic acid and maintaining the mixture for a period ranging from 1 hour to 1 month at a temperature ranging from 10 to 80° C., the organic peracid polymer-containing composition containing an organic peracid polymer (2 to 50% by weight) and, in some cases, the hydrogen peroxide (2 to 50% by weight) and the inorganic acid (0.1 to 10% by weight) is obtained.