Abstract: At least one of a Rh catalyst, a Pd catalyst or a Ru catalyst is used as a catalyst in preparing the salt of &ggr;-(piperidyl)-butyric acid (2) by hydrogenating the salt of &ggr;-(pyridyl)butyric acid (1) [preferably the salt of &ggr;-(pyridyl)butyric acid (1) obtained in the undermentioned steps (a) and (b) and containing not more than 3% by weight of salt of bis(pyridylethyl)acetic acid (3)] in a solvent in the presence of a catalyst: (a) reacting the vinylpyridine (4) with the diester of malonic acid (5) in the presence of a base to give the 2-(pyridylethyl)malonic acid diester (6), and (b) hydrolyzing and decarboxylating the 2-(pyridylethyl)malonic acid diester (6) obtained in the step (a) in an acidic aqueous solution to give the salt of &ggr;-(pyridyl)butyric acid (1).