A SAW filter device includes a SAW filter chip in which one-port surface acoustic wave resonators each including an IDT made of Al or an Al alloy, are provided on a .theta.-rotated Y-cut X-propagation LiNbO.sub.3 substrate. The cutting angle .theta. of the .theta.-rotated Y-cut X-propagation LiNbO.sub.3 substrate is in the range between about 50.degree. and about 55.degree.. The normalized film thickness of the IDT 100h/.lamda. (%) (h denotes the thickness of the IDT and .lamda. denotes the wavelength of a surface acoustic wave) is in the range between about 2% and about 4%. The duty ratio of the IDT is equal to or less than about 0.4.