An acoustic thin film resonator including: a first piezoelectric thin film 101; a pair of primary electrodes 103 and 104 for applying an electric signal, which are formed on the first piezoelectric thin film; a second piezoelectric thin film 102 that is disposed so that an oscillation generated in the first piezoelectric thin film propagates to the second piezoelectric thin film; a pair of secondary electrodes 104 and 105 for outputting an electric signal, which are formed on the second piezoelectric thin film; a load 108 that is connected between the secondary electrodes; and a control portion 109 that controls a value of the load. Thereby, an acoustic thin film resonator element is formed so that an electric signal inputted from the primary electrodes is outputted from the secondary electrodes by a piezoelectric effect, and a resonant frequency and an antiresonant frequency are made variable through the control of the value of the load. A resonant frequency and an antiresonant frequency are made variable at the same time without resonant characteristics being deteriorated.