A longitudinally coupled resonator type surface acoustic filter includes a rotated Y-cut X-propagating LiTaO.sub.3 substrate. The gap length G in the IDT electrode of the surface acoustic wave resonator is about 0.3 times the wavelength .lamda. of the surface acoustic wave or less. The gap length G is the spacing between the bus bars tips of the electrode fingers extending from one bus bar (electrode terminal) toward the other opposing bus bar of the IDT electrode included in the surface acoustic wave filter.