Abstract: In a medical instrument sterilizing and washing method and apparatus for sterilizing and washing a medical instrument in a short time without corroding the metal forming the medical instrument to be washed. The sterilizing and washing method comprises the steps of preparing an electrolytic aqueous solution by adding and dissolving a halide composed of a bromide compound as a simple substance or a bromide compound and other halogenated compound to and in tap water; directly subjecting the electrolytic aqueous solution to electrolysis through electrode plates composed of an anode and a cathode and generating electrolytically-generated water containing hypohalogenous acid; and sterilizing and washing the medical instrument with the electrolytically-generated water while maintaining the hydrogen ion concentration (pH) in the electrolytic water to at least 6 at all times.