PURPOSE: To decide optimum start control time by considering the end of a holiday in which an air conditioner is not used by referring to an advancing pattern at the end of the holiday different from a weekday advancing pattern to calculate advancing time in the case of a service.

CONSTITUTION: When an operator sets an indoor target temperature, a room using time, etc., on a setting board 4, a CPU 1 compares a calendar 1-3 with holiday end data written from a disk 2 in a memory 3 by a comparator 1-1, and judges whether it is the end of the holiday or not. In the case of the end of the holiday, the CPU 1 extracts an advancing pattern for the end of the holiday held in the disk 2, and decides the starting time of an air conditioner 5A by referring to a temperature difference between an indoor temperature measured by a sensor 6A and the indoor target temperature and the advancing pattern for the end of the holiday. The conditioner 5A is started according to the decision to obtain an optimum environment at room use starting time.