Private insurance system compensates the social insurance system that is organized and operated by the government. It covers the losses from various economic risks. But there are many disputes between the insurer and the insured. One of them is the dispute out of non notice of the address change of the insured. In the most contract terms of the insurer, there is regulation that asks for the notice of the change of the address of the insured. It regards the non notice as a arrival of the declaration when the insurer send mail to the last known address. We can compare the legal situation between Korea and Germany. Germany has reformed its insurance contract law(VVG) in the year of 2007 severely. Germany has the regulation(§ 13 VVG) that regards the sending registered mail as arrived, when the insurance contractor did not notice the alteration of his address and the change of name. The Korean supreme court asks for a kind of address detection duty to the insurer. The German Civil Law Code(BGB)(§ 308, Nr. 6) and the Korean standard contract terms act(§ 12) have also such a regulation. But the German insurance contract law has special regulation in § 13 VVG. The Korean Commercial Code does not have such a special regulation. This difference leads to the minute difference in the interpretation of the dispute case. In the case of A company, the insurance contractor did not notice the real address of the insured. But the insured called the call center of the A company. In the discussion process, the consultant recognized the change of the hand phone number of the insured. But the counselor and the life planer in charge of the company did not take following-up measure. This means a kind of negligence of the A company. Therefore in such a case, the insurer should give insurance money to the insured. The absence of the detection efforts can be namely in that case accepted. The insurance contract was not namely effectively cancelled. The insurance company should effort to get real address of the insured with the greatest care in the future.