A thin-film piezoelectric acoustic wave resonator that has a large k2, can trap acoustic energy in a resonating part, does not excite spurious resonance, or can finely adjust resonance frequency and a high-frequency filter using the thin-film piezoelectric acoustic wave resonator are provided without increasing the number of processes. At both ends of a vibrating part (1), fixing parts (8) are physically connected, and between the vibrating part (1) and each of the fixing parts (8), an acoustic insulating part (10) and a phase rotating part (11) are physically connected. As with the vibrating part (1), the acoustic insulating part (10) and the phase rotating part (11) are made up of an upper metal film (3), a piezoelectric thin film, and a lower metal film, and an acoustic wave reflector (6) is provided on each of an upper surface, a lower surface, and side surfaces of the vibrating part (1), the acoustic insulating part (10), and the phase rotating part (11). The vibrating part (1) has a width smaller than its length (La) and also smaller than its thickness, and width/thickness is smaller than 1.