an ultrasonic sensor for detecting an object includes : a substrate ; a transmission device for transmitting an ultrasonic wave ; a plurality of reception devices for receiving the ultrasonic wave ; and a circuit for processing received ultrasonic waves , which are received by the reception devices after the ultrasonic wave transmitted from the transmission device is reflected by the object . the transmission device and the reception devices are integrated into the substrate . the dimensions of the sensor are minimized , and detection accuracy of the sensor is improved .