PURPOSE: To provide a draft measuring device for a ship capable of measuring a draft of the ship from the outside without contacting the ship which is sailing to pass a lock gate and coming alongside a quay.

CONSTITUTION: A device comprises a reflecting type draft sensor 1 having a plurality of ultrasonic wave transceiving elements 1-1 provided in the bottom part of a waterway, water level gage 2 and a decision part 3 for measuring a distance from the bottom part of a ship 4 passing a water area to the bottom part of the water from an output of the draft sensor 1 to calculate a draft value obtained of the ship 4 passing the waterway from the distance and a water level measured by the water level gage 2.