PURPOSE : To improve the efficiency of real estate intermediary business by simply and efficiently preparing documents necessary for the transaction of a real estate or the contract of leasing and a guide book for the renewal of a lease contract to a lessor and a lessee. CONSTITUTION : When an object to be contracted is specified by an object specifying means C, minimum data necessary for the contract are inputted by a contracting procedure data inputting means E and a document to be prepared is selected by a preparing document selecting means D, the format and fixed data of the selected document are read out from a contract document format storing means B, printing data are prepared by a contract document printing data preparing means F based upon the data of the specified object which are stored in an uncontracted object data storing means A and the inputted data and printed out by a contract document printing means G to prepare the document necessary for the contract.