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.SolutionProvided is a sulfonamide derivative having a coumarin skeleton represented by the following formula (I) and having various substituents: wherein R1, R2, R3, R4, R5, R6 and R7 are the same as defined in the specification, and a salt thereof.