Provided is a compound showing excellent antifungal activity against Trichophyton fungus, which is a major causative microorganism of superficial mycosis, and high effectiveness on diseases caused by Trichophyton fungi. A biaryl derivative represented by the formula (I) or a salt thereof: wherein ring A is an optionally substituted phenyl, or an optionally substituted 5- or 6-membered ring heteroaryl (ring A may be further condensed to form an optionally substituted fused ring)； Q is CH 2 , C=O, NH, O, S or the like； X 1 , X 2 and X 3 are CR 1 or N； Y is CH or N； Z is CR 2b or N； R 2a and R 2b are each a hydrogen atom, a halogen atom, an optionally substituted C 1 -C 6 alkyl group, a C 1 -C 6 haloalkyl group or the like； R 2a and R 2b may form, together with carbon atoms bonded thereto, an optionally substituted carbocycle, or an optionally substituted heterocycle.
