A unidirectional transducer for a SAW filter having a first group (D) including electrode finger (21) and electrode fingers (14) and (16) arranged at center distances of 3&lgr;/8 and 5&lgr;/8 in a direction opposite to the propagation direction of the surface acoustic wave from electrode finger (21); a second group (E) including electrode fingers (22), (15) and (20) arranged at center distances of 10&lgr;/8, 13&lgr;/8 and 15&lgr;/8 in the propagation direction from electrode finger (21); and a third group (F) including electrode fingers (17), (18) and (19) arranged at center distances of 3&lgr;/8, 5&lgr;/8 and 7&lgr;/8 in the propagation direction from electrode finger (21).