To provide a manufacturing method for an ammonium carboxylate that permits efficient reduction of the amount of by-products of the reaction in an aqueous solution of the ammonium carboxylate to give the ammonium carboxylate of high purity.

The manufacturing method for an ammonium carboxylate comprises hydrolyzing a nitrile compound (C) in the presence of an enzyme (B) having nitrilase activity, where the enzyme (B) is one obtained by secretory production using a bacterium in the presence of a surfactant (A). Preferably, the surfactant (A) is at least one selected from the group consisting of an amphoteric surfactant, an anionic surfactant and a nonionic surfactant having an HLB of 0-13.