To make it possible to obtain effective data that can correctly manage an ability of an air conditioner by limiting a range for which the maximum value, the minimum value and an average value of measured value measured at plural times are obtained to a time slot when a building facility related to the measured value operates.

When an air conditioner related to a measured value starts operating (S11), it waits until a temperature and humidity in a room maintains a given value (S12), and stores a time at that time (S13). The time is made an 'operation starting time' of the air conditioner (S14). Then, when the air conditioner stops operating (S15), it waits until the time (S16), since the temperature and humidity in the room still maintain the given value, and stores a time at that time (S17). Thus, as the 'operation starting time' and an 'operation stop time' can be detected, the maximum value, the minimum value and an average value within a time range detected are calculated.