PROBLEM TO BE SOLVED : To provide a system by which a risk in the real estate company is reduced and the company is made to immediately cope with damage or the like of a facility caused by increase of tenants, by keeping balance between rental incomes of a real estate company and an owner by correlating a master lease income with an occupation rate in a real estate object master-leased from the owner. SOLUTION : A master lease course based on agreement information of the owner read out from an owner database is read out of a master lease course database by a master lease course setting means, real estate object information is read out of a real estate object database based on the agreement information, the number of tenants corresponding to the real estate object is read out of a tenant database, and the real estate object information, the occupation rate and the sub-lease course are inquired to calculate a sub-lease income by a master lease income calculating means. COPYRIGHT : (C)2004, JPO