[Object] To provide an ultrasonic urine volume measuring instrument that can highly accurately measure urine volume of a measurement subject and that is convenient for the measurement subject. [Solution] There are provided a mode selector 22a capable of selecting one of a measurement mode of measuring urine volume while an ultrasound probe 10 is placed at a certain measurement position on the stomach of a measurement subject, and a positioning mode of measuring urine volume while moving the ultrasound probe 10 to a plurality of tentative measurement positions on the stomach in order to determine the measurement position suitable for placing the ultrasound probe 10 in the measurement mode and an index value memory 23a that stores a maximum value among urine volumes at the plurality of tentative measurement positions, calculated by the arithmetic unit 24, while the positioning mode is being selected, and/or an allowance value determined on the basis of the maximum value. The maximum value and/or the allowance value is displayed, on a graph on a display unit 27, as a positioning index value for positioning the ultrasound probe 10.
