A ship maneuver supporting device capable of displaying a collision risk zone which matches navigation feel of a ship operator with reduced calculation load, is provided. The ship maneuver supporting device 1 includes processing circuitry (11, 21, 31, 41). The processing circuitry calculates a collision risk value for determining whether a collision risk zone that is a zone where a possibility of a collision between a first ship and a second ship will occur in the future is high is to be displayed, based on a separating distance between the position of the second ship estimated at a plurality of future time points and the position of the first ship estimated corresponding thereto, in consideration of a physical size of at least one of the first ship and the second ship. Further, the processing circuitry generate display data for displaying the collision risk zone at the estimated position of the second ship, based on the determination using the collision risk value.