An ultrasonic device that transmits and receives ultrasonic waves includes: ultrasonic elements including first and second surfaces from which the ultrasonic waves are emitted； and a backing unit that supports the second surfaces of the ultrasonic elements and attenuates the ultrasonic waves emitted to the second surface side. The backing unit has slits inclined in a thickness direction. The ultrasonic elements are arranged in the shape of an array, and the slits are arranged at distances equal to an arrangement distance between the ultrasonic elements arranged in the shape of an array.
