4-OXYBENZOPYRAN DERIVATIVE

PROBLEM TO BE SOLVED: To obtain a therapeutic agent for arhythmia. SOLUTION: This therapeutic agent for arhythmia comprises a 4- oxybenzopyran derivative of formula (I) [R1 and R2 are each independently a hydrogen atom, a 1-6C alkyl group or a phenyl group; R3 is a hydroxyl group or a 1-6C alkylcarbonyloxy group; R4 is a hydrogen atom, a 3-6C cycloalkyl group a 1-6C alkyl group, a 1-6C alkylcarbonyl group, a 1-6C alkylaminocarbonyl group, a di 1-6C alkylaminocarbonyl group, an aryl group or a hetero aryl group; n is an integer of 0 to 4; X is C(=O)NR7, NR8, NH(=O)NH or S(O)2NH; R5 is a hydrogen atom or a group of formula (II); R6 is a hydrogen atom, a halogen atom, a nitro group or a cyano group] or its pharmaceutically acceptable salt as an active ingredient.