A water-soluble metal-working oil agent, characterized by comprising a component A, a component B, a component C, and a component D, wherein: the component A is an ester compound which has a characteristic temperature, as measured in accordance with JIS K2242, of 570°C or higher and which is contained in the water-soluble metal-working oil agent in an amount of 10 mass% or more with respect to the entire amount of the agent; wherein component A is a carboxylic acid polyol ester compound, wherein the carboxylic acid forming the ester compound is one selected from the group consisting of myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, oleic acid, elaidic acid, erucic acid, nervonic acid, linoleic acid, y-linolenic acid, arachidonic acid, α-linolenic acid, stearidonic acid, and eicosapentaenoic acid. the component B is at least one condensed fatty acid which is selected from a condensed fatty acid, produced through dehydration condensation of a hydroxycarboxylic acid, and a condensed fatty acid, produced through dehydration condensation of an alcoholic hydroxyl group of the condensed fatty acid with a monovalent carboxylic acid, which has a characteristic temperature, as measured in accordance with JIS K2242, of 650°C or higher, and which is contained in the water-soluble metal-working oil agent in an amount of 7.5 mass% or more with respect to the entire amount of the agent; the component C is a carboxylic acid which is contained in the water-soluble metal-working oil agent in an amount of 2 mass% or more with respect to the entire amount of the agent; and the component D is a basic compound contained in such a neutralization equivalent that at least the component B and component C are neutralized to cancel out the sum of the acid values thereof. the component A is an ester compound which has a characteristic temperature, as measured in accordance with JIS K2242, of 570°C or higher and which is contained in the water-soluble metal-working oil agent in an amount of 10 mass% or more with respect to the entire amount of the agent; wherein component A is a carboxylic acid polyol ester compound, wherein the carboxylic acid forming the ester compound is one selected from the group consisting of myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, oleic acid, elaidic acid, erucic acid, nervonic acid, linoleic acid, y-linolenic acid, arachidonic acid, α-linolenic acid, stearidonic acid, and eicosapentaenoic acid. the component B is at least one condensed fatty acid which is selected from a condensed fatty acid, produced through dehydration condensation of a hydroxycarboxylic acid, and a condensed fatty acid, produced through dehydration condensation of an alcoholic hydroxyl group of the condensed fatty acid with a monovalent carboxylic acid, which has a characteristic temperature, as measured in accordance with JIS K2242, of 650°C or higher, and which is contained in the water-soluble metal-working oil agent in an amount of 7.5 mass% or more with respect to the entire amount of the agent; the component C is a carboxylic acid which is contained in the water-soluble metal-working oil agent in an amount of 2 mass% or more with respect to the entire amount of the agent; and the component D is a basic compound contained in such a neutralization equivalent that at least the component B and component C are neutralized to cancel out the sum of the acid values thereof.