To provide a disinfectant eliminating problems about safety of liquefied chlorine, operation efficiency and equipment, decomposability of sodium hypochlorite, maintainability, aggregation and lowering of disinfecting effects by shifting to the alkalinity and enhancing the safety, operation efficiency and maintainability, responsive with simple equipment and preventing the aggregation and lowering of the disinfecting effects by shifting to the alkalinity in relation to disinfection of water to be disinfected, to provide a method for disinfecting using the same and to provide an apparatus for disinfection.

The apparatus for disinfection is equipped with an apparatus 1 for producing chlorine hydrate, a storage tank 2 for the chlorine hydrate and a feed pump 3 for the chlorine hydrate and is designed to feed the chlorine hydrate to a flow channel 4 for the water to be disinfected with the feed pump 3 to disinfect the water to be disinfected. A static mixer 5 is provided in the course of the flow channel 4 for the water to be disinfected to rapidly dissolve the chlorine hydrate.