The present invention provides a novel sulfonamide compound having a ribonucleotide reductase inhibitory activity or a salt thereof, and a pharmaceutical composition containing the same as an active ingredient. A compound represented by Formula (I) [wherein, X 1 represents an oxygen atom or the like； X 2 represents an oxygen atom； X 3 represents -NH-； X 4 represents a hydrogen atom or the like； R 1 represents -C(R 11 )(R 12 )- or the like； R 11 and R 12 are the same or different and each represents a hydrogen atom or the like； R 2 represents an optionally substituted C 6 -C 14 aromatic hydrocarbon group or the like； R 3 represents an optionally substituted C 6 -C 14 aromatic hydrocarbon group or the like； R 4 represents a hydrogen atom or the like] or a salt thereof.
