The present invention provides a crystal of 6-(3-chloro-2-fluorobenzyl)-1-((S)-1-hydroxymethyl-2-methylpropyl]-7-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylic acid, which shows a particular powder X-ray diffraction pattern of a characteristic diffraction peaks at diffraction angles 2θ(°) as measured by powder X-ray diffractometry. The crystal of the present invention is superior in physical and chemical stability.
