A SAW filter, an antenna sharing device using the same, and a mobile communication terminal using the same, the power-resistance of which is high and the isolation of which between transmission and reception is ensured. The filter is a ladder SAW filter comprising alternately series arms each having at least one SAW resonator connected in series to a signal path and parallel arms each having at least one SAW resonator connected between the signal path and the ground. The size of the wiring patterns of the parallel arms is smaller than that of the series arms. Even when the filter is used as a seried arm input type, the inductance component of the parallel arm wiring pattern can be small, and therefore the reflectance in the blocking band is large.