PURPOSE: To enable an easy removal of a driving element of an air filter driving device by a method wherein a shape memory alloy is applied as the driving element.

CONSTITUTION: An air filter driving device 8 for use in removing an air filter 3 out of an air feeding circuit is arranged. A driving element 9 composed of a shape memory alloy is fixed in the air-filter driving device 8. When the air filter 3 is to be removed, a switch 11 is turned ON and the shape memory alloy of the driving element 9 may generate heat due to its internal resistance. When the shape memory alloy generates heat, its full length is extended. Since the driving device 8 is contacted with the upper end of the frame of the air filter 3, if the full length is extended, the air filter 3 is pushed out. The projection provided at the lower part of the air filter 3 is removed from the air filter presser projection 4 and dropped down and the air filter 3 is descended to a substantial low position so that the air filter may easily be removed.