A SAW device comprises a substrate, input and output interdigital electrodes provided on the substrate alternately to form a row of electrodes, and a pair of open strip reflectors disposed at both ends of the row, the input interdigital electrodes having a first pair number representing the number of pairs of opposing finger electrodes forming the input electrode, the output interdigital electrodes having a second pair number representing the number of pairs of opposing finger electrodes forming the output electrode, wherein the first pair number and second pair number are set different in the adjacent input and output electrodes with a predetermined ratio therebetween, the first pair number is changed in each input electrodes in the row, and the second pair number is changed in each output electrodes in the row.