An acoustic matching layer is formed on individual ultrasonic transducer elements on a base. Electric conductors are arranged between adjacent ultrasonic transducer elements, the electric conductors being connected to electrodes of the ultrasonic transducer elements. Protective films overlap the electric conductors. The protective films have smaller moisture permeability than the acoustic matching layer. Wall portions are arranged on the protective films, the wall portions separating portions of the acoustic matching layer that are respectively located on adjacent ultrasonic transducer elements from each other at least in a part of a height range with respect to a height direction from the base, and having an acoustic impedance that is different from the acoustic impedance of the acoustic matching layer.