In an input section (30), a set temperature Ts which becomes a control target temperature of a humidity controller (10), and a set relative humidity Rs which becomes a control target humidity of the humidity controller (10) are set. An air conditioning control section (42) adjusts the temperature adjusting capacity of the humidity controller (10) such that the room temperature may come very close to the set temperature Ts. Further, an arithmetic section (33) calculates, as the target absolute humidity As, the absolute humidity which becomes the relative humidity set value Rs at the set temperature Ts. A humidity adjustment section (41) adjusts the humidity adjusting capacity of the humidity controller (10) such that the absolute humidity of the room may come very close to the target absolute humidity As.