PURPOSE: To obtain filter characteristics with a small shape factor and deep trap by providing a 2nd converter differing in center frequency at a position where no interference with an elastic surface wave generated by a 1st converter is caused.

CONSTITUTION: On the surface of piezoelectric body 1, 1st input elastic surface wave converter 2 is provided and on a propagation path for an elastic surface wave generated by converter 2, 1st output elastic surface wave converter 3 is provided. Further, 2nd elastics surface wave converter 4 is provided where the elastic surface wave of converter 2 does not interfere. Although center frequency f1 of 1st converter 2 is not equal to center frequency f2 of 2nd converter 4, they are coupled through matching circuits 6 and 7 respectively and then connected to signal sourse 5. An output appears in load 8 connected to 1st output elastic surface wave converter 3.