A surface acoustic wave filter includes first to fifth IDTs arranged on a
piezoelectric substrate along a surface acoustic wave propagation
direction. The second IDT and the fourth IDT have a phase difference of
180.degree. with respect to each other. The second and fourth IDTs are
connected to an unbalanced terminal. The third IDT includes a first
sub-IDT portion and a second sub-IDT portion. The first IDT and the first
sub-IDT portion are connected to a first balanced terminal, and the
second sub-IDT portion and the fifth IDT are connected to a second
balanced terminal. The following conditions:
1.55.ltoreq.N3/N1.ltoreq.2.58 and N1=N5 are satisfied, where N1 denotes
the number of electrode fingers that determines the center frequency of
the first IDT, N3 denotes the number of electrode fingers that determines
the center frequency of the third IDT, and N5 denotes the number of
electrode fingers that determines the center frequency of the fifth IDT.