PURPOSE: To change and control a flow rate and pressure without causing efficiency drop by changing and controlling the distance between the tip of a fan edge and an impeller, in response to the instructed flow rate in a cross flow fan.

CONSTITUTION: The distance between the tip of an edge 14 and the periphery of an impeller 1 is altered by sliding the edge 14 with solenoid 12h, 12i, 13k, 13l. The difference between the actual air quantity from an airflow sensor and a target airflow is calculated and the position of the edge is controlled by a signal corresponding to the difference. Thus, the flow rate of a fluid in an air duct can be controlled easily and reliably.