PROBLEM TO BE SOLVED: To provide a thin ultrasonic transducer element chip having strength enduring pressing force in a thickness direction of a substrate.SOLUTION: In an ultrasonic transducer element chip, a substrate 21 is disposed with openings 45 in an array state. In a first face of the substrate 21, each opening 45 is provided with an ultrasonic transducer element 23. A reinforcing member 52 is fixed on a second face on the opposite side of the first face of the substrate 21. The reinforcing member 52 reinforces the substrate 21. Groove parts 53 form ventilation passages communicating an inner space of the opening parts 45 and an outer space of the substrate 21.SELECTED DRAWING: Figure 4
