To measure simply and accurately hydraulic information of rivers or lakes.

This measuring device for the hydraulic information of rivers or lakes is equipped with ultrasonic sensors 503, 504 for irradiating an ultrasonic beam toward the bottom of a river or a lake under a measuring line set in the river or the lake, and detecting a reflected wave of the ultrasonic beam from the bottom, a rotation mechanism 505 for rotating the ultrasonic beam in the measuring line direction, a means for changing an ultrasonic frequency of the ultrasonic beam, corresponding to the time from irradiation of the ultrasonic beam until detection of the reflected wave, a propulsion mechanism 502 for moving the ultrasonic sensors along the measuring line, a position sensor 507 for determining the position on the measuring line of the ultrasonic sensors, and a means for calculating the position of the bottom along the measuring line from the irradiation direction of the ultrasonic beam, the positions of the ultrasonic sensors 503, 504, the time from irradiation of the ultrasonic beam until detection of the reflected waves, and the speed of the ultrasonic beam in the water of the river or in the water of the lake.