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, X1 represents an oxygen atom or the like； X2 represents an oxygen atom； X3 represents —；NH—；； X4 represents a hydrogen atom or the like； R1 represents —；C(R11)(R12)—； or the like； R11 and R12 are the same or different and each represents a hydrogen atom or the like； R2 represents an optionally substituted C6-C14 aromatic hydrocarbon group or the like； R3 represents an optionally substituted C6-C14 aromatic hydrocarbon group or the like； R4 represents a hydrogen atom or the like] or a salt thereof.
