A duct type air conditioning system includes an air conditioner; a plurality of ducts that are disposed in a plurality of air-conditioned spaces that are supplied with conditioned air of the air conditioner; a plurality of room temperature sensors that are disposed in the air-conditioned spaces; a control device that controls the air conditioner; and controllers that control the air conditioner. The control device determines a room temperature sensor disposed in any of the air-conditioned spaces on which an air-conditioning starting operation is performed by the controllers by using sensor setting information in which the air-conditioned spaces and the room temperature sensors are associated with each other. The air conditioner includes an air-conditioning control degree calculating unit that calculates a degree of control of the air conditioner on the basis of a room temperature detected by the room temperature sensor determined by the control device.