Provided is an ultrasonic transducer including: a housing including a bottom surface and side members, the side members facing each other and extending upwardly with a space part therebetween, the housing having an opened upper part; a piezoelectric resonator disposed at an upper portion of the bottom surface; a housing auxiliary member disposed at upper portions of the side members and inserted into the space part; and a signal connection pin part disposed at an upper portion of the housing auxiliary member. In particular, the housing auxiliary member is formed of material having a lower density than the housing, thereby improving isotropic radiation characteristics. Sides of the housing are symmetrically opened by a structure for the ultrasonic transducer so that an isotropic radiation angle of ultrasonic waves is maximized to improve accuracy of sensing an obstacle, an internal structure of the housing is simplified in such a way that no additional process is required, thereby reducing manufacturing cost, and the housing auxiliary member is combined with the opened part of the housing so that external pollution can be prevented from entering into the ultrasonic transducer.