An apparatus for measuring an amount of urine in a bladder using ultrasonic signals comprises: a transducer a switch for selecting one of operational modes, which include a preliminary scan mode and a scan mode a transducer drive unit for driving the transducer and a central control unit for operating according to the operational mode to provide an amount of urine in the bladder. The central control unit in the preliminary scan mode acquires the ultrasonic signals for a single scan plane from the transducer, generates a 2-dimensional B-Mode ultrasonic image using the acquired ultrasonic signals, displays the B-Mode ultrasonic image, and marks a vertical center-line on the B-Mode ultrasonic image. The central control unit in the scan mode acquires ultrasonic signals for a plurality of scan planes from the transducer, measures an amount of urine in the bladder using the acquired ultrasonic signals, and provides the amount of urine.
