Provided is a compound showing high effectiveness to diseases caused by Trichophyton, by having an excellent antifungal activity against Trichophyton which is the main causative bacterium of superficial mycoses.The biaryl derivatives represented by formula (I) or their salts: wherein, ring A represents an optionally substituted phenyl or an optionally substituted 5- or 6-membered heteroaryl (the ring A may further condense to form an optionally substituted condensed ring； Q represents CH2, C=O, NH, O or S, etc.； X1, X2 and X3 are CR1 or N； Y is CH or N； Z is CR2b or N； R2a and R2b are hydrogen atom, halogen atom, an optionally substituted C1-C6 alkyl group, C1-C6 haloalkyl group, etc., and the R2a and R2b may form an optionally substituted carbocyclic ring or an optionally substituted heterocyclic ring with the carbon atom to which they are attached.本發明提供對表在性真菌症的主要原因菌的白癬菌具有優異的抗真菌活性的化合物，該化合物對起因於白癬菌的疾患表現高有效性。通式(I)表示的聯芳衍生物或其鹽：[式中，環A表示可經取代的苯基，或可經取代的5或6員環雜芳基(該環A亦可再縮合而形成可經取代的縮合環)；Q是CH2、C=O、NH、O或S等；X1、X2及X3是CR1或N；Y是CH或N；Z是CR2b或N；R2a及R2b是氫原子，鹵原子、可經取代的C1-C6烷基、C1-C6鹵烷基等；R2a及R2b亦可與該等鍵結的碳原子一起，形成可經取代的碳環，或可經取代的雜環]。
