Provided is a novel compound or a salt thereof inhibiting MTHFD2 and useful for treating a disease caused by overexpression of MTHFD2, a disease involved in overexpression of MTHFD2 and/or a disease associated with overexpression of MTHFD2.[Solution]Provided is a sulfonamide derivative having a coumarin skeleton represented by the following formula (I) and having various substituents:wherein R, R, R, R, R, Rand Rare the same as defined in the specification,and a salt thereof.