The present invention provides novel phenoxyacetic acid derivatives represented by the general formula: ##STR1## wherein R.sup.1 represents a hydroxy group, a lower alkoxy group, an aralkoxy group, an amino group, or a mono or di(lower alkyl)amino group; one of R.sup.2 and R.sup.3 is a hydrogen atom, a halogen atom, a lower alkyl group or a lower alkoxy group, while the other is a hydrogen atom; R.sup.4 represents a halogen atom, a lower alkyl group, a halo(lower alkyl) group, a hydroxy group, a lower alkoxy group, an aralkoxy group, a cyano group, a nitro group, an amino group, a mono or di(lower alkyl)amino group, a carbamoyl group, a mono or di(lower alkyl)carbamoyl group or a group represented by the general formula: --NHCOR.sup.5 (wherein R.sup.5 represents a hydrogen atom or a lower alkyl group); the carbon atom marked with (R) represents a carbon atom in R configuration; and the carbon atom marked with (S) represents a carbon atom in S configuration, and pharmaceutically acceptable salts thereof, which have excellent .beta..sub.3 -adrenoceptor stimulating effects and are useful as agents for the prevention or treatment of obesity, hyperglycemia, the diseases caused by intestinal hypermotility, pollakiuria, urinary incontinence, depression, or the diseases caused by biliary calculi or hypermotility of biliary tract.