PURPOSE: To make the mode coupled SAW filter provided with an impedance matching circuit small in size.

CONSTITUTION: An input side interdigital electrode IDTi and an output side interdigital electrode IDTo arranged opposite to each other on a piezoelectric substrate are respectively divided into multi-taps Ti0-Tin and To0-Ton, and number of taps Ni at the input side is made not equal to number of taps No at the output side to obtain a desired input output impedance. That is, the connected tap number at the input side and the output side is adjusted to obtain the desired input output impedance to make the numbers unequal to each other. Thus, the impedance is adjusted, the impedance matching circuit is formed by the same manufacture process together with the SAW filter on the piezoelectric substrate and miniaturization is attained.