This ultrasonic transducer element chip is characterized by being provided with: a substrate having openings arranged in an array ultrasonic transducer elements disposed at each of the openings on a first surface of the substrate and a reinforcing member that is fixed to a second surface of the substrate which is on the opposite side of the first surface of the substrate and reinforces the substrate. The ultrasonic transducer element chip is further characterized in that the reinforcing member has linear grooves by which the internal space of the openings and the external space of the substrate communicate with each other said linear grooves being positioned side by side in a first direction on a plane of said surface on a surface that is fixed to the second surface of the substrate at intervals that are smaller than the width of the openings in the first direction on the second surface of the substrate.
