Provided is a reducing composition for permanently reshaping keratin fibers such as hair, prepared by mixing a component A and a component B at the time of use, wherein the component A comprises at least one thiol-based reducing compound and has pH 7.0 or less； the component B comprises at least one buffer salt selected from the group consisting of carbonates, bicarbonates and carbamates, and has pH 8.0 or more； at least one of the component A and component B comprises at least one disulfide compound； and the prepared reducing composition has pH ranging from 7.0 to 7.8.
