This paper describes the development of a process for end milling of aluminum alloy, using electrolyzed reduced water of dilute sodium chloride solution instead of the dry cutting. Dry process cutting is applied to the process of precision instruments where great surface cleanliness is essential. However, when using dry process cutting, it comes into question how to prevent the cutting temperature from rising, and the tool from wearing promptly. There is every possibility that electrolyzed reduced water is adaptable to the processing of the precision instrument, because it does not contain oils and fats, and excels in the cooling operation. First, we experimented in dry cutting, cutting using electrolyzed reduced water or cutting fluid. Next, we evaluated the cut surface cleanliness, surface roughness of cutting surface, the cutting temperature, and the tool wear. By this study, the following matters became clear. (1) The cutting surface layer which is done with electrolyzed reduced water is clearer than the one which is done by dry process cutting surface. And passivity layer was formed on the cutting surface which is done with electrolyzed reduced water. (2) If using electrolyzed reduced water, we can prevent the tool point of a blade from agglutinating. (3) The cutting temperature which is caused by the cutting using electrolyzed reduced water is low. (4) When the material is small, the surface roughness value of the cut surface which is done with electrolyzed reduced water is bigger than the one which is done by dry process cutting.