A ultrasonic device detecting a direction to an object includes: a transmitting element of a ultrasonic wave; first and second receiving elements; a diffraction wave phase detector; an initial phase memory for an initial phase of a diffraction wave; a sound speed detector; a phase correction amount calculator calculating a phase shift caused by a sound speed change and calculating a phase correction amount based on the phase of the diffraction wave, the initial phase and the phase shift; a phase correction element correcting a phase of the reflection wave based on the phase correction amount; and a direction detector for detecting the direction to the object based on a difference between corrected phases of the reflection wave received by the first and second receiving elements, a distance between the first and second receiving elements, and a wavelength of the transmission ultrasonic wave corresponding to a sound speed.