An amidine compound represented by formula (I) (wherein A1 represents a nitrogen atom or a group represented by formula CR6; A2 and A3 are the same as or different from each other and independently represent a nitrogen atom or a group represented by formula CH; R1 represents an aryl group which may be substituted by 1 to 5 substituents independently selected from a substituent group (2) or the like; R2 and R3 are the same as or different from each other and independently represent a hydrogen atom, a halogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group or a C1-6 alkoxy group; and R4 and R5 are the same as or different from each other and independently represent a hydrogen atom, a C1-6 haloalkyl group, a C1-6 alkyl group or the like) or a salt thereof. The compound is useful as an anti-fungal agent.