<p>The present invention is a filter and duplexer that are equipped with: series oscillators (S1-S4); parallel oscillators (P1-P4) that are formed on a piezoelectric substrate (10) and that are connected in parallel to the series oscillators (S1-S4); a inductor (L3) that is connected in series to a parallel oscillator (P4); a capacitor (C1) that is formed on the piezoelectric substrate (10) and connected in parallel to the inductor (L3), and wiring (18) that is formed on the piezoelectric substrate (10) and that connects the parallel oscillator (P4) and the capacitor (C1).</p>
