PURPOSE: To prepare the titled compound useful as a lubricant additive, etc., economically, in an industrial scale, easily, from a reaction system obtained by the dehydration reaction of a halogenated carboxylic acid with metal oxide or metal hydroxide using a saturated aliphatic hydrocarbon as a solvent.

CONSTITUTION: One or more halogenated carboxylic acids and one or more metal oxides or metal hydroxides are subjected to dehydration reaction in a solvent comprising a saturated aliphatic hydrocarbon or its mixture having a boiling point of preferably about 50W180°C, especially 60W150°C. After the reaction, the product is separated from the solvent to obtain a halogenated carboxylic acid metal salt useful as a flame retardant, raw material of plastics, additives, etc. in addition to the above-mentioned use. Since the compound can be separated from the solvent easily in the form of crystal, and the solvent can be reused without purification by e.g. simple distillation, fractional distillation, etc., the process is industrially advantageous.