To inexpensively and stably supply a derivative having a 2-acylaminopyridine configuration represented by Formula (I) in an amount required as a pest controlling agent, the present invention provides a process of producing a compound represented by Formula (B) by acylating a 2-positioned amino group of a compound represented by Formula (A) by using an acylation agent [where, Ar is a phenyl group or a 5-6 membered hetero ring, R1 is a C1-C6 alkyl group, and Y is a hydrogen atom, a halogen atom, a hydroxyl group, a C1-C6 alkyl group which may be substituted with a halogen atom, a C1-C6 alkoxy group which may be substituted with a halogen atom, a cyano group, a formyl group, or a nitro group], and also provides a method including further alkylating a 1-position nitrogen atom of the compound represented by Formula (B).
