PURPOSE: To calculate the charge for every air conditioner by integrating the operation time by air volume notches for every air conditioner and calculating charge, for the data obtained by an operation state input means.

CONSTITUTION: An air conditioning mode detection means 28 and an air volume notch detection means 29 within a controller 3 incorporated into each air conditioner 2 detect the states of the air conditioning modes of each air conditioner 2 and the air volume notch, the states are inputted in an operation state output means 4, the data is outputted, and monently inputted to the operation state input means 5 of central unit 1 via a data transmission line 12. The integrated operation time of each air conditioner 2 is counted by the operation time integration means 26 of the central device and the usage charge of the air conditioner 2 tenant is calculated by a charge calculation means 7 by multiplying the integrated operation time by a coefficient. Thus, even when a tenant changes and the partition between two rooms changes, the charging of the usage charge of the air conditioner for every tenant can be easily changed.