In this paper, checking out a various problems in the accounting and the allocation of the common cost in the management of apartment in order to find out the right way of the management, I have tried to build a standard management system for the apartment and study the effect expected by the computerizing. To develop the software to computerize the management of the apartment, which is the main task of this paper, I have checked out a various problems and then computerized a standard system to better the unreliable management and somewhat doubtful accounting process and correct the inaccuracy in the allocation of the common cost.