An energy-trapping-type thickness extensional piezoelectric resonator using a thickness extensional vibration mode having first and second resonance electrodes formed on portions of the top surface and the bottom surface of a piezoelectric substrate that is polarized in the thickness direction thereof, respectively, in which a portion where the first and second resonance electrodes oppose each other is formed as an energy-trapping-type vibration section, wherein, in order to suppress frequency changes of the thickness extensional vibration mode due to temperature, which is a main response using resonance characteristics, a suppression response having a frequency-temperature-change tendency for suppressing frequency changes of the main response due to temperature is brought into close proximity with the main response.