A fused benzeneoxyacetic acid derivative of the formula (I): ##STR1## R.sup.1 is OH, alkoxy, (alkyl)amino, residue of an amino acid; A is phenyl, alkyl substituted by phenyl, residue of an imidazole, imidazole-2-yloxy(thio), 2-oxoimidazole, pyrazole, oxadiazole, oxazole, triazole, isoxazole or isothiazole, in the group of benzene may be substituted by one to three of alkyl, alkoxy, halogen, nitro or trihalomethyl; e is 3-5; f is 1-3; p is 1-4; q is 0-2; r is 1-4; s is 0-3) and salts thereof possess an agonistic on PGI.sub.2 receptor, so it is useful for prevention and/or treatment of thrombosis, arteriosclerosis, inchemic heart diseases, gastric alcer and hypertention.