To obtain an alkali cleaning water having comparable cleaning performance to commercially available detergents and to provide a method and a device for manufacturing the cleaning water.

Electrolytic alkali water produced in the cathode chamber 2 of an electrolytic cell 1 by electrolysis is adjusted to 0.003 mol/l to 0.02 mol/l alkali concentration and 0.3 to 0.05 of alkali ratio.