An NC-program conversion device includes an OCR processing unit that recognizes a character string from an input image; a first storage unit that stores one alphabetic letter and the number of digits of a number subsequent to the alphabetic letter, in an associated manner; a second storage unit that stores a program code that is composed of a combination of one alphabetic letter and a two-character number and an effective character that is composed of one alphabetic letter subsequent to the program code, in an associated manner; and a character-string segmenting unit that refers to the first storage unit and the second storage unit, to segment each line of the character string, which is recognized by the OCR processing unit, as program codes stored in the first storage unit in an associated manner.