This article deals with the insurer can revoke the insurance contract. The Supreme Court Decision 2000.1.11, 99na33311 concerns a case where even though the insurer asked on the insurance application form a specific question whether the applicant had had insurance policies, the latter with lots of other policies, the latter with lots of other policies did not answer it. The Supreme Court held in favour of the applicant on the ground that the insurer failed to prove that he was fraudulent or grossly negligent. This article argues: since the Korean Commercial Code sec. 651-2 provides that the fact about which a specific question is put is presumed as material, the applicant, the applicant was deemed to know the materiality of the existence of other insurance; the applicant with so many policies cannot be heard to assert his ignorance of other insurances. Second, the insurance contracts at issue had an express term that when the insured makes new contracts he notify the insurer of the fact. Despite this the insured failed to make such an notice. The Supreme Court held that only the insured who made a fraudulent or grossly negligent non-notification is subject to insured was neither fraudulent nor grossly negligent. The suggested reason was that the duty of notification must be treated equally with the duty of disclosure. However, this article argues that it seems groundless.