An ink data modification method configured for a handwritten character string, the method comprising: a step of acquiring ink data, wherein the ink data includes stroke data input by a user, wherein the stroke data is data including a series of coordinates indicating a locus of a designated position of a stylus, a determination step of determining a modification method of the ink data by detecting a spelling error included in a handwritten character string represented by the ink data; and a modification step of modifying the ink data by manipulating the ink data on a basis of the modification method, wherein the modification method is to add a character, and the manipulation of the ink data by the modification step includes an operation of adding one or more pieces of stroke data representing a character to be added to a plurality of pieces of stroke data configuring the ink data, or wherein the modification method is to delete a character, and the manipulation of the ink data by the modification step includes an operation of deleting one or more pieces of stroke data corresponding to a character to be deleted from the plurality of pieces of stroke data configuring the ink data, or wherein the modification method is to replace a character, and the manipulation of the ink data by the modification step includes: an operation of deleting, from a plurality of pieces of stroke data configuring the ink data, one or more pieces of stroke data corresponding to an erroneous character, and an operation of adding one or more pieces of stroke data representing a correct character to the plurality of pieces of stroke data configuring the ink data. a step of acquiring ink data, wherein the ink data includes stroke data input by a user, wherein the stroke data is data including a series of coordinates indicating a locus of a designated position of a stylus, a determination step of determining a modification method of the ink data by detecting a spelling error included in a handwritten character string represented by the ink data; and a modification step of modifying the ink data by manipulating the ink data on a basis of the modification method, wherein the modification method is to add a character, and the manipulation of the ink data by the modification step includes an operation of adding one or more pieces of stroke data representing a character to be added to a plurality of pieces of stroke data configuring the ink data, or wherein the modification method is to delete a character, and the manipulation of the ink data by the modification step includes an operation of deleting one or more pieces of stroke data corresponding to a character to be deleted from the plurality of pieces of stroke data configuring the ink data, or wherein the modification method is to replace a character, and the manipulation of the ink data by the modification step includes: an operation of deleting, from a plurality of pieces of stroke data configuring the ink data, one or more pieces of stroke data corresponding to an erroneous character, and an operation of adding one or more pieces of stroke data representing a correct character to the plurality of pieces of stroke data configuring the ink data. an operation of deleting, from a plurality of pieces of stroke data configuring the ink data, one or more pieces of stroke data corresponding to an erroneous character, and an operation of adding one or more pieces of stroke data representing a correct character to the plurality of pieces of stroke data configuring the ink data.