This ship desulfurization device, for desulfurizing an exhaust gas discharged from an exhaust gas generating device mounted on a ship, is provided with: an absorption tower including an absorption tower body part which defines an inner space having a longitudinal direction, and in which an exhaust gas introduction port that communicates with the inner space is formed in an end on one side in the longitudinal direction; and an exhaust gas introducing device for guiding the exhaust gas discharged from the exhaust gas generating device to the absorption tower body part. In addition, when the maximum length of the inner space of the absorption tower body part in the longitudinal direction is L, and the maximum width of the inner space of the absorption tower body part in the short-length direction perpendicular to the longitudinal direction is W, the ratio of the maximum width W to the maximum length L (W:L) is in the range of greater than 1:1.1 and equal to or less than 1:6.0.