PURPOSE: To offer an effective means on evaluation of operating conditions of an equipment, by calculating inner product values between characteristic vectors corresponding to characteristic values and various element data and using them as an index of overall evaluation of operation of the equipment.

CONSTITUTION: Various elements required for grasping equipment operating conditions such as the equipment operating time, each stop time, and the output are measured for a prescribed time, and an interrelation coefficient matrix of various element data and characteristic values and characteristic vectors of this matrix are calculated. A prescribed number of characteristic vactors corresponding to characteristic values are selected in order of characteristic values. Inner product values between characteristic vectors corresponding to characteristic values and various element data are calculated and are used as the index of overall evaluation of operation of the equipment. Since operating conditions of the equipment are evaluated overall with a high reliability, an effective means is offered on evaluation of operating conditions of the equipment.