A ship maneuver supporting device, comprising: an other ship data acquiring module that is configured to acquire information on a position and a velocity (Vt) of a second ship; an other ship future position estimating module that is configured to estimate, based on the position and the velocity (Vt) of the second ship acquired by the other ship data acquiring module, future positions (D1,..., D5) of the second ship at a plurality of future time points when the second ship continues traveling on the same course at the same traveling speed; a ship data acquiring module that is configured to acquire information on a position and a velocity of a first ship; a ship future position estimating module that is configured to estimate, based on the position and the velocity of the first ship acquired by the ship data acquiring module, for each of the future positions (D1,..., D5) of the second ship and at the same future time point at which said future position of the second ship has been estimated, a plurality of future positions (P1,..., P5) that the first ship could reach when the first ship continues traveling on a course arbitrarily defined at the position of the first ship, at the same traveling speed; a risk calculating module that is configured to calculate for each of the future positions (D1,..., D5) of the second ship a collision risk value for determining whether a collision risk zone that is a zone where a possibility of a collision between the first ship and the second ship will occur in the future is high is to be displayed, based on a separating distance (R1,..., R5) between the future position (D1,..., D5) of the second ship and the closest future position (P1,..., P5) of the first ship estimated at the same future time point as said future position (D1,..., D5) of the second ship; and a display data generating module that is configured to generate display data for displaying the collision risk zone at the estimated future position (D1,..., D5) of the second ship, based on the determination using the collision risk value. an other ship data acquiring module that is configured to acquire information on a position and a velocity (Vt) of a second ship; an other ship future position estimating module that is configured to estimate, based on the position and the velocity (Vt) of the second ship acquired by the other ship data acquiring module, future positions (D1,..., D5) of the second ship at a plurality of future time points when the second ship continues traveling on the same course at the same traveling speed; a ship data acquiring module that is configured to acquire information on a position and a velocity of a first ship; a ship future position estimating module that is configured to estimate, based on the position and the velocity of the first ship acquired by the ship data acquiring module, for each of the future positions (D1,..., D5) of the second ship and at the same future time point at which said future position of the second ship has been estimated, a plurality of future positions (P1,..., P5) that the first ship could reach when the first ship continues traveling on a course arbitrarily defined at the position of the first ship, at the same traveling speed; a risk calculating module that is configured to calculate for each of the future positions (D1,..., D5) of the second ship a collision risk value for determining whether a collision risk zone that is a zone where a possibility of a collision between the first ship and the second ship will occur in the future is high is to be displayed, based on a separating distance (R1,..., R5) between the future position (D1,..., D5) of the second ship and the closest future position (P1,..., P5) of the first ship estimated at the same future time point as said future position (D1,..., D5) of the second ship; and a display data generating module that is configured to generate display data for displaying the collision risk zone at the estimated future position (D1,..., D5) of the second ship, based on the determination using the collision risk value.