An ultrasonic oscillator unit (68, 268) comprising: an ultrasonic oscillator array in which a plurality of ultrasonic oscillators are arranged outward in a semicylindrical shape; an electrode part having a plurality of electrodes, each of two parts of the electrode part being provided on a respective portion of the back surface of the ultrasonic oscillator array opposite the arrangement surface of the plurality of ultrasonic oscillators and being electrically connected to the plurality of ultrasonic oscillators, respectively, wherein each portion is adjacent a respective end surface side of the ultrasonic oscillator array perpendicular to the arrangement surface; a backing material layer (102, 202) that is disposed on the back surface of the ultrasonic oscillator array serving as an inside with respect to said arrangement surface of the plurality of ultrasonic oscillators, wherein each of the two parts of the electrode part is disposed within a gap between the backing material layer (102, 202) and the back surface at a corner of the backing material layer (102, 202) at a respective side thereof; and a cable wiring part in which a plurality of cables are respectively disposed on a plurality of wiring lines electrically connected to the plurality of electrodes of the electrode part, wherein the width of the backing material layer (102, 202) becomes smaller toward the side of the backing material layer opposite to said arrangement surface of the plurality of ultrasonic oscillators such that (i) the backing material layer has a stepwise stepped part that becomes thinner toward a side opposite to the arrangement surface, on each side surface of the backing material layer in the width direction thereof or (ii) the backing material layer has an inclined part that becomes thinner in an inclined fashion toward the side opposite to the arrangement surface, on each side surface of the backing material layer in the width direction thereof, and wherein the cable wiring part is provided along the width of the backing material layer (102, 202) such that the cable wiring part is disposed on side surfaces of the backing material layer (102, 202) in the width direction thereof. an ultrasonic oscillator array in which a plurality of ultrasonic oscillators are arranged outward in a semicylindrical shape; an electrode part having a plurality of electrodes, each of two parts of the electrode part being provided on a respective portion of the back surface of the ultrasonic oscillator array opposite the arrangement surface of the plurality of ultrasonic oscillators and being electrically connected to the plurality of ultrasonic oscillators, respectively, wherein each portion is adjacent a respective end surface side of the ultrasonic oscillator array perpendicular to the arrangement surface; a backing material layer (102, 202) that is disposed on the back surface of the ultrasonic oscillator array serving as an inside with respect to said arrangement surface of the plurality of ultrasonic oscillators, wherein each of the two parts of the electrode part is disposed within a gap between the backing material layer (102, 202) and the back surface at a corner of the backing material layer (102, 202) at a respective side thereof; and a cable wiring part in which a plurality of cables are respectively disposed on a plurality of wiring lines electrically connected to the plurality of electrodes of the electrode part, wherein the width of the backing material layer (102, 202) becomes smaller toward the side of the backing material layer opposite to said arrangement surface of the plurality of ultrasonic oscillators such that (i) the backing material layer has a stepwise stepped part that becomes thinner toward a side opposite to the arrangement surface, on each side surface of the backing material layer in the width direction thereof or (ii) the backing material layer has an inclined part that becomes thinner in an inclined fashion toward the side opposite to the arrangement surface, on each side surface of the backing material layer in the width direction thereof, and wherein the cable wiring part is provided along the width of the backing material layer (102, 202) such that the cable wiring part is disposed on side surfaces of the backing material layer (102, 202) in the width direction thereof.