The ultrasonic sensor

1. An ultrasonic sensor comprising: a piezoelectric element, a plurality of which are arranged in a grid pattern in a predetermined direction, with electrodes provided on both surfaces that transmit and receive an ultrasonic wave; ! at least two acoustic matching layers provided on one surface of the piezoelectric element; ! a plurality of first grooves that are provided in the piezoelectric element and at least the first acoustic matching layer on the piezoelectric element of the at least two acoustic matching layers, and divide at least the piezoelectric element in a lengthwise direction orthogonal to an array direction of the piezoelectric element ; ! a signal conductor provided on a surface on the opposite side from the one surface of the piezoelectric element; and! a plurality of second grooves that separate at least the first acoustic matching layer of the at least two acoustic matching layers, the piezoelectric element, and the signal conductor in an array direction of the piezoelectric element! wherein the acoustic matching layer, piezoelectric element, and signal conductor are curved surfaces in the longitudinal direction of the piezoelectric element. ! 2. An ultrasonic sensor comprising: a piezoelectric element, a plurality of which are arranged in a grid pattern in a predetermined direction, with electrodes provided on both surfaces that transmit and receive an ultrasonic wave; ! at least two acoustic matching