A novel compound which is a 1,3-dihydro-2H-indol-2-one derivative represented by the formula (1): (1) (wherein R1 represents halogeno, C1-4 alkyl, etc. and R2 represents hydrogen, halogeno, etc., or R2 is present in the 6-position of the indol-2-one and is bonded to R1 to form C3-6 alkylene; R3 represents halogeno, hydroxy, etc. and R4 represents hydrogen, halogeno, C1-4 alkyl, etc., or R4 is present in the 3-position of the phenyl and is bonded to R3 to form methylenedioxy; R5 represents hydrogen or fluorine; R6 represents ethylamino, dimethylamino, etc.; R7 represents C1-4 alkoxy; and R8 represents C1-4 alkoxy) or a pharmaceutically acceptable salt of the derivative. The compound has antagonistic activity against an aruginine-vasopressin V1b receptor.