A knit designing system for designing a knitted fabric to be knitted by a flat knitting machine, based on design data containing knitting codes being information on stitches constituting the knitted fabric, the knit designing system including: an input unit for a user to edit design data; a display unit for displaying the design data as a design sheet on which cells are arranged in a grid into a wale and a course direction, a knitting code being assigned to each cell; a first creation unit that creates, based on paper-pattern data indicating a contour of the knitted fabric, original data (6, 60) being the design data of the knitted fabric including a contour line corresponding to a contour line of the paper-pattern data, the created contour line being formed by connecting straight lines extending in the wale direction to straight lines extending in the course direction; and a first memory that stores the original data, the knit designing system characterized by: a second memory that stores a line module including information regarding a plurality of minute lines for constituting a revised contour line suitable for knitting and an order of arrangement of the minute lines, wherein the minute line is one of a straight line extending in the wale direction, a straight line extending in the course direction, and a combination of a straight line extending in the wale direction and a straight line extending in the course direction; a second creation unit that creates, based on the line module, a plurality of candidate lines obtained by varying the number of each of the plurality of minute lines; and a specifying unit that compares the contour line of the original data with each of the plurality of candidate lines, and specifies one of the plurality of candidate lines that is most approximate to the contour line of the original data as an approximation line. an input unit for a user to edit design data; a display unit for displaying the design data as a design sheet on which cells are arranged in a grid into a wale and a course direction, a knitting code being assigned to each cell; a first creation unit that creates, based on paper-pattern data indicating a contour of the knitted fabric, original data (6, 60) being the design data of the knitted fabric including a contour line corresponding to a contour line of the paper-pattern data, the created contour line being formed by connecting straight lines extending in the wale direction to straight lines extending in the course direction; and a first memory that stores the original data, the knit designing system characterized by: a second memory that stores a line module including information regarding a plurality of minute lines for constituting a revised contour line suitable for knitting and an order of arrangement of the minute lines, wherein the minute line is one of a straight line extending in the wale direction, a straight line extending in the course direction, and a combination of a straight line extending in the wale direction and a straight line extending in the course direction; a second creation unit that creates, based on the line module, a plurality of candidate lines obtained by varying the number of each of the plurality of minute lines; and a specifying unit that compares the contour line of the original data with each of the plurality of candidate lines, and specifies one of the plurality of candidate lines that is most approximate to the contour line of the original data as an approximation line. a second memory that stores a line module including information regarding a plurality of minute lines for constituting a revised contour line suitable for knitting and an order of arrangement of the minute lines, wherein the minute line is one of a straight line extending in the wale direction, a straight line extending in the course direction, and a combination of a straight line extending in the wale direction and a straight line extending in the course direction; a second creation unit that creates, based on the line module, a plurality of candidate lines obtained by varying the number of each of the plurality of minute lines; and a specifying unit that compares the contour line of the original data with each of the plurality of candidate lines, and specifies one of the plurality of candidate lines that is most approximate to the contour line of the original data as an approximation line.