An ultrasonic sensing device is foldable and includes two bracket portions rotatably connected and an ultrasonic sensor on each bracket portion. The ultrasonic sensor includes a flexible circuit board carrying an ultrasonic signal transmitting element and an ultrasonic signal receiving element. The ultrasonic signal transmitting element is mounted to one of the two bracket portions, and the ultrasonic signal receiving element is mounted to other of the two bracket portions. The ultrasonic signal transmitting element is capable of rotating to the ultrasonic signal receiving element by opening and closing the two bracket portions.
