An ultrasonic sensor includes a substrate, three or more ultrasonic arrays and a control unit. The three or more ultrasonic arrays are disposed on a surface of the substrate. The control unit is configured to control ultrasonic waves transmitted from the ultrasonic arrays. Each of the three or more ultrasonic arrays includes a linear array structure has a plurality of ultrasonic elements arranged in a corresponding one of three or more straight lines, with the three or more straight lines collectively enclosing a closed area on a plane that contains the surface of the substrate. The control unit is configured to control the ultrasonic waves transmitted from each of the three or more ultrasonic arrays so that the ultrasonic waves are transmitted within a scanning plane that contains the corresponding one of the three or more straight line and that is perpendicular to the surface of the substrate.