An ultrasonic urine volume measuring instrument includes an ultrasound probe, an ultrasound controller that controls transmission and reception of ultrasound and its reflected waves, and an arithmetic unit that calculates urine volume in the bladder on the basis of the reflected waves. The arithmetic unit includes a comparator that compares the calculated urine volume in the bladder with a first threshold. The ultrasound measurement cycle becomes a longer cycle when the urine volume in the bladder is less than the first threshold, compared to the urine volume being greater than or equal to the first threshold. The ultrasonic urine volume measuring instrument includes a timer unit capable of causing, when the urine volume in the bladder compared by the comparator is less than the first threshold, the arithmetic unit to enter a sleep state during each measurement cycle, and causes the arithmetic unit to recover every measurement cycle.
