An ultrasonic sensor (100, 200) comprising: a case having a bottom portion; and a piezoelectric element that is bonded to an inner surface of the bottom portion and that performs bending vibration together with the bottom portion, wherein the piezoelectric element includes: a piezoelectric layer having a transmission region and a reception region; a specific electrode (30, 90) that functions as either a common bus or a ground electrode; a transmission electrode opposing the specific electrode with the transmission region interposed between the transmission electrode and the specific electrode; and a reception electrode opposing the specific electrode with the reception region interposed between the reception electrode and the specific electrode; wherein the transmission region and the reception region are formed at positions adjacent to each other; characterised in that: the impedance between the transmission electrode and the specific electrode is different from the impedance between the reception electrode and the specific electrode; and the impedance between the transmission electrode and the specific electrode is lower than the impedance between the reception electrode and the specific electrode. a case having a bottom portion; and a piezoelectric element that is bonded to an inner surface of the bottom portion and that performs bending vibration together with the bottom portion, wherein the piezoelectric element includes: a piezoelectric layer having a transmission region and a reception region; a specific electrode (30, 90) that functions as either a common bus or a ground electrode; a transmission electrode opposing the specific electrode with the transmission region interposed between the transmission electrode and the specific electrode; and a reception electrode opposing the specific electrode with the reception region interposed between the reception electrode and the specific electrode; a piezoelectric layer having a transmission region and a reception region; a specific electrode (30, 90) that functions as either a common bus or a ground electrode; a transmission electrode opposing the specific electrode with the transmission region interposed between the transmission electrode and the specific electrode; and a reception electrode opposing the specific electrode with the reception region interposed between the reception electrode and the specific electrode; wherein the transmission region and the reception region are formed at positions adjacent to each other; characterised in that: the impedance between the transmission electrode and the specific electrode is different from the impedance between the reception electrode and the specific electrode; and the impedance between the transmission electrode and the specific electrode is lower than the impedance between the reception electrode and the specific electrode. the impedance between the transmission electrode and the specific electrode is different from the impedance between the reception electrode and the specific electrode; and the impedance between the transmission electrode and the specific electrode is lower than the impedance between the reception electrode and the specific electrode.