PROBLEM TO BE SOLVED: To provide a method of dyeing or decoloring hair which is excellent in applicability when applying the agent to the hair so that agent is easily spread over a whole head, and which adheres the hair at the lower edge of the hair to each other after application to be capable of preventing a floating state of a bundle of hairs at the lower edge of the hair.SOLUTION: A method of dyeing or decoloring hair comprises the steps of: (1) mixing a first agent containing an alkali material and a second agent containing hydrogen peroxide in a container body of a non-aerosol foamer container to prepare mixed liquor； (2) attaching a non-aerosol foamer to the container body and discharging the mixed liquor prepared in the step (1) from the non-aerosol foamer container as foamy matter； (3) applying the foamy matter to the hair by hand； and (4) kneading the foamy matter on the hair with hand to increase complex elastic modulus Gof the foamy matter which is 3 times or more and 10 times or less as that of the foamy matter when discharged at the step (2).
