A management system of a machine equipped with a driving-power source reads out maintenance conditions from a storage means of maintenance management information when data and conditions, concerned about a maintenance management of a machine, the features of the machine, and so on, including the maintenance conditions, are inputted from the input means. Then, information about predicted maintenance management under a certain operation time of the machine is predicted with reference to the maintenance conditions. Subsequently, the information about the predicted maintenance management is represented on a display means. Furthermore, a maintenance predicted value is previously stored in a data base or the like with respect to the maintenance within an operation time under the contract or within a contract term for each of a plurality of contract ranks. A maintenance actual result value of the machine being entered is accumulatively stored. After a termination of the maintenance contract of the machine, the maintenance predicted value that corresponds to a model and a contract rank of the machine is read out, and simultaneously the maintenance actual result value of the machine is read out, followed by making a judgment whether the maintenance actual result value is larger or smaller than the maintenance contract predicted value.