An ultrasonic oscillator unit comprising: an ultrasonic oscillator array in which a plurality of ultrasonic oscillators having a rod shape are arranged in a circular-arc shape while aligning in a longitudinal direction of the rod shape; an electrode part that is provided on at least one end surface of the plurality of ultrasonic oscillators perpendicular to the longitudinal direction and has a plurality of electrodes electrically connected to the plurality of ultrasonic oscillators, respectively; a circular-arc backing material layer that is disposed on a rear surface of the ultrasonic oscillator array that becomes a center side of the circular-arc shape; and a cable wiring part including a flexible printed wired board in which a plurality of cables are disposed at a plurality of wiring lines electrically connected to the plurality of electrodes of the electrode part, a staircase part that is disposed to abut against a lower surface of the backing material layer, is perpendicular to a width direction of the backing material layer along the longitudinal direction of the rod shape, and becomes stepwise in the width direction of the backing material layer from an ultrasonic oscillator side at one end part of the ultrasonic oscillator array toward an ultrasonic oscillator side on the other end part thereof with respect to the lower surface of the backing material layer, wherein the flexible printed wired board extends to a lower side of the backing material layer that becomes a side opposite to the ultrasonic oscillator array and is separated into a plurality of belt-like pieces in a comb shape, wherein the cable wiring part has a cable connecting part including, in a comb shape, a plurality of strip-like electrode parts that are provided in the plurality of belt-like pieces, and wherein each of the strip-like electrode parts is formed by linearly disposing at least one electrode pad in a longitudinal direction of each of the belt-like pieces on each belt-like piece, wherein a portion above the cable connecting part of the cable wiring part is disposed along the backing material layer, wherein the plurality of belt-like pieces of the flexible printed wired board are bent along the lower surface of the backing material layer, are bent at respective steps of the staircase part again, and are disposed along the respective steps of the staircase part, and wherein the plurality of strip-like electrode parts of the cable connecting part are respectively disposed on the belt-like pieces disposed along the respective steps of the staircase part. an ultrasonic oscillator array in which a plurality of ultrasonic oscillators having a rod shape are arranged in a circular-arc shape while aligning in a longitudinal direction of the rod shape; an electrode part that is provided on at least one end surface of the plurality of ultrasonic oscillators perpendicular to the longitudinal direction and has a plurality of electrodes electrically connected to the plurality of ultrasonic oscillators, respectively; a circular-arc backing material layer that is disposed on a rear surface of the ultrasonic oscillator array that becomes a center side of the circular-arc shape; and a cable wiring part including a flexible printed wired board in which a plurality of cables are disposed at a plurality of wiring lines electrically connected to the plurality of electrodes of the electrode part, a staircase part that is disposed to abut against a lower surface of the backing material layer, is perpendicular to a width direction of the backing material layer along the longitudinal direction of the rod shape, and becomes stepwise in the width direction of the backing material layer from an ultrasonic oscillator side at one end part of the ultrasonic oscillator array toward an ultrasonic oscillator side on the other end part thereof with respect to the lower surface of the backing material layer, wherein the flexible printed wired board extends to a lower side of the backing material layer that becomes a side opposite to the ultrasonic oscillator array and is separated into a plurality of belt-like pieces in a comb shape, wherein the cable wiring part has a cable connecting part including, in a comb shape, a plurality of strip-like electrode parts that are provided in the plurality of belt-like pieces, and wherein each of the strip-like electrode parts is formed by linearly disposing at least one electrode pad in a longitudinal direction of each of the belt-like pieces on each belt-like piece, wherein a portion above the cable connecting part of the cable wiring part is disposed along the backing material layer, wherein the plurality of belt-like pieces of the flexible printed wired board are bent along the lower surface of the backing material layer, are bent at respective steps of the staircase part again, and are disposed along the respective steps of the staircase part, and wherein the plurality of strip-like electrode parts of the cable connecting part are respectively disposed on the belt-like pieces disposed along the respective steps of the staircase part.