In a balanced-type surface acoustic wave filter, IDTs in the center of
each of first and second longitudinally coupled resonator type surface
acoustic wave filter sections are connected to an unbalanced input
terminal, first and third IDT sections on both the sides of the center
IDT are connected to first and second balanced output terminals,
respectively, the first and third IDTs have narrow pitch electrode finger
sections N, and when an electrode finger pitch of the narrow pitch
electrode finger section of the second IDT is P1, an electrode finger
pitch of the narrow pitch electrode finger section of the first and third
IDTs is P2, the number of electrode fingers of the second IDT except for
the narrow pitch electrode finger section of the IDT is K1, and the
number of electrode fingers of the first and third IDT except for the
narrow pitch electrode finger section is K2, P1>P2 and
1.12.ltoreq.K1/K2.ltoreq.1.65 are satisfied.