This invention relates to a compound represented by the following formula (1) : its salt or a hydrate thereof. R 1 represents hydrogen atom, an optionally substituted alkyl group containing 1 to 6 carbon atoms, a cycloalkyl group containing 3 to 6 carbon atoms, or a substituted carbonyl group derived from an amino acid, a dipeptide, or a tripeptide R 2 represents hydrogen atom, an optionally substituted alkyl group containing 1 to 6 carbon atoms, or a cycloalkyl group containing 3 to 6 carbon atoms R 3 represents an alkyl group containing 1 to 6 carbon atoms or a halogen-substituted alkyl group containing 1 to 6 carbon atoms R 4 represents a cycloalkyl group containing 3 to 6 carbon atoms or a halogen-substituted cycloalkyl group containing 3 to 6 carbon atoms R 5 represents hydrogen atom, phenyl group, acetoxymethyl group, pivaloyloxymethyl group, ethoxycarbonyl group, choline group, dimethylaminoethyl group, 5-indanyl group, phthalidyl group, 5-alkyl-2-oxo-1,3-dioxol-4-ylmethyl group, 3-acetoxy-2-oxobutyl group, or a phenylalkyl group comprising an alkylene group containing 1 to 6 carbon atoms and phenyl group X 1 and X 2 independently represent hydrogen atom or a halogen atom and X represents hydrogen atom or a halogen atom. This compound exhibits broad and strong antibacterial activity to both Gram positive and Gram negative bacteria as well as high safety, and therefore, this compound is useful as a quinolone antibacterial drug, and a prophylactic and/or therapeutic drug for an infectious disease.
