The present invention relates to a manufacturing method for a window opening for a ship, which can prevent the deformation or breakage of a window opening due to welding or cutting during the assembling process of a ship. The manufacturing method for a window opening for a ship is to manufacture a window opening composed of a straight unit and a corner unit, and comprises as follows: a corner unit cutting step (S1) which cuts the corner unit (310) of a window member (200) forming the window opening (300); a combining step (S2) which combines the window member (200) wherein the cut corner unit (310) is cut with the hull (100) of a ship; and a straight unit cutting step (S3) which cuts the straight unit (320) of the window opening (300) in the window member (200) combined with the hull (100). [Reference numerals] (S1) Corner unit cutting step;(S2) Combining step;(S3) Straight unit cutting step
