A filter comprising two cascaded primary-tertiary longitudinal coupling dual-mode SAW filters provided so as to flatten the passband of the filter and three IDT electrodes arranged with electrode finger pitches L1 so as to decrease the VSWR below 2, wherein the pitch L2 of the central IDT electrodes of one of the dual-mode SAW filters is larger than the pitch L1, electrode fingers are symmetrically removed from both sides of the IDT electrode, and the removed electrode fingers are connected to the opposed IDT electrode so as to use them as dummy electrodes with pitches L2.