The present invention provides an anti-fungal agent having an excellent anti-fungal action and excellent physicochemical properties such as safety and solubility in water. The present invention discloses a compound represented by the following formula (I) or a salt thereof:[wherein R1 represents a hydrogen atom, a halogen atom, an amino group, R11-NH-(wherein R11 represents a C1-6 alkyl group, a hydroxy C1-6 alkyl group, a C1-6 alkoxy C1-6 alkyl group or a C1-6alkoxycarbonyl C1-6 alkyl group), R12-(CO)-NH- (wherein R12 represents a C1-6 alkyl group or a C1-6 alkoxy C1-6 alkyl group), a C1-6 alkyl group, a hydroxy C1-6 alkyl group, a cyano C1-6 alkyl group, a C1-6 alkoxy group or a C1-6 alkoxy C1-6 alkyl group or a phosphonoamino group R2 represents a hydrogen atom, a C1-6 alkyl group, an amino group or a di C1-6 alkylamino group or a phosphonoamino group one of X and Y is a nitrogen atom while the other is a nitrogen atom or an oxygen atom ring A represents a 5- or 6-member heteroaryl ring or a benzene ring which may have a halogen atom or 1 or 2 C1-6 alkyl groups Z represents a single bond, a methylene group, an ethylene group, an oxygen atom, a sulfur atom, -CH2O-, -OCH2-, -NH-, -CH2NH-, -NHCH2-, -CH2S- or -SCH2- R3 represents a hydrogen atom or a halogen atom or a C1-6 alkyl group, a C3-8 cycloalkyl group, a C6-10 aryl group, a 5- or 6-member heteroaryl group or a 5- or 6-member nonaromatic heterocyclic group which may have 1 or 2 substituents and R4 represents a hydrogen atom or halogen atom provided that either R1 or R2 represents a phosphonoamino group.]
