An apparatus comprising: a) an acquisition unit configured to acquire a plurality of work information about a calibration of one or more instruments performed at different dates and times by a maintenance apparatus configured to perform the calibration of the one or more instruments, the instrument being a measuring device in a plant; b) an extraction unit configured to extract a plurality of data elements including instrument identification information and a calibration result from the work information, the work information including target instrument information and calibration work information, the work information being related to maintenance work performed for multiple times on each instrument, the plurality of data elements having a predetermined output format; c) a generation unit configured to calculate a measurement error for each instrument based on the calibration result from the plurality of data elements in a period of time and to generate an output information including an instrument identification information and said measurement error, the measurement error preferably including a maximum measurement error; d) a storage processing unit configured to store, on a storage device, the output information generated by the generation unit; and e) a display processing unit configured to acquire the output information from the storage processing unit and to display a change with time of the measurement error of the one of the instruments, presenting the tendency of the aging degradation of the measurement error, per calibration points, of the one of the instruments, or a change with time of the maximum measurement error of the one of the instruments, presenting the tendency of the aging degradation of the maximum measurement error of each of the one or more instruments. a) an acquisition unit configured to acquire a plurality of work information about a calibration of one or more instruments performed at different dates and times by a maintenance apparatus configured to perform the calibration of the one or more instruments, the instrument being a measuring device in a plant; b) an extraction unit configured to extract a plurality of data elements including instrument identification information and a calibration result from the work information, the work information including target instrument information and calibration work information, the work information being related to maintenance work performed for multiple times on each instrument, the plurality of data elements having a predetermined output format; c) a generation unit configured to calculate a measurement error for each instrument based on the calibration result from the plurality of data elements in a period of time and to generate an output information including an instrument identification information and said measurement error, the measurement error preferably including a maximum measurement error; d) a storage processing unit configured to store, on a storage device, the output information generated by the generation unit; and e) a display processing unit configured to acquire the output information from the storage processing unit and to display a change with time of the measurement error of the one of the instruments, presenting the tendency of the aging degradation of the measurement error, per calibration points, of the one of the instruments, or a change with time of the maximum measurement error of the one of the instruments, presenting the tendency of the aging degradation of the maximum measurement error of each of the one or more instruments. a change with time of the measurement error of the one of the instruments, presenting the tendency of the aging degradation of the measurement error, per calibration points, of the one of the instruments, or a change with time of the maximum measurement error of the one of the instruments, presenting the tendency of the aging degradation of the maximum measurement error of each of the one or more instruments.