Provided is a 1,3,4 oxadiazole 2 carboxamide compound which has STAT3 inhibitory activity and is useful as an anticancer agent. Specifically disclosed is a 1,3,4 oxadiazole 2 carboxamide compound represented by formula (I) or a pharmacologically acceptable salt thereof. (In the formula Ar represents a furyl group or the like R represents a hydrogen atom or the like and X Y represents a diaryl group such as a biphenyl group.)