The present invention provides a water-glycol hydraulic fluid comprising 0.3-0.6% by mass in total of fatty acid sodium salt and/or fatty acid, and 0.3-0.6% by mass of dimerized fatty acid. The water-glycol hydraulic fluid also comprises 20-60% by mass water, 20-60% by mass glycol, 0.01-0.06% by mass alkali hydroxide compound selected from potassium hydroxide and/or sodium hydroxide, and 1.0-5.0% by mass alkanolamine.
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