A method of manufacturing footwear, comprising an upper made up of independent pieces, said method comprising the steps of: a) cutting the pieces (7, 8) that will form the upper of the footwear; b) preparing a mold and counter-mold, between which there is demarcated a space corresponding to the volume of the upper and underpart, which mold is made up of two or more parts (1, 2) which internally reproduce the outer configuration of the footwear and have areas (4, 5) the contour of which correspond to that of the pieces that will form the upper of the footwear, and the counter-mold of which adopts the shape of a metal last and demarcates with the inner surface of the pieces forming the mold a volume corresponding to that of the upper and underpart of the footwear; c) placing the pieces (7, 8) that will form the upper of the footwear in the areas (4, 5) defined inside the mold, from which they project to demarcate empty cavities and channels; d) injecting a thermoplastic material in molten state into the mold until filling all the cavities formed between mold and counter-mold, as well as the channels demarcated by the pieces (7, 8) that will form the upper and coming into contact with said pieces (7, 8); e) opening the mold and extracting the last constituting the counter-mold; the method of manufacturing footwear characterized in that - the aforementioned areas (4, 5) are demarcated by ribs of a height less than the thickness of the pieces (7, 8) that will form the upper, which ribs are separated from the surface of the last when the mold is closed; - and in that the channels delimited between opposing edges of consecutive pieces (7, 8) are of a height less than the thickness of the pieces (7, 8) that will form the upper, and said channels widen toward the flesh side of the upper. a) cutting the pieces (7, 8) that will form the upper of the footwear; b) preparing a mold and counter-mold, between which there is demarcated a space corresponding to the volume of the upper and underpart, which mold is made up of two or more parts (1, 2) which internally reproduce the outer configuration of the footwear and have areas (4, 5) the contour of which correspond to that of the pieces that will form the upper of the footwear, and the counter-mold of which adopts the shape of a metal last and demarcates with the inner surface of the pieces forming the mold a volume corresponding to that of the upper and underpart of the footwear; c) placing the pieces (7, 8) that will form the upper of the footwear in the areas (4, 5) defined inside the mold, from which they project to demarcate empty cavities and channels; d) injecting a thermoplastic material in molten state into the mold until filling all the cavities formed between mold and counter-mold, as well as the channels demarcated by the pieces (7, 8) that will form the upper and coming into contact with said pieces (7, 8); e) opening the mold and extracting the last constituting the counter-mold; the method of manufacturing footwear characterized in that - the aforementioned areas (4, 5) are demarcated by ribs of a height less than the thickness of the pieces (7, 8) that will form the upper, which ribs are separated from the surface of the last when the mold is closed; - and in that the channels delimited between opposing edges of consecutive pieces (7, 8) are of a height less than the thickness of the pieces (7, 8) that will form the upper, and said channels widen toward the flesh side of the upper. - the aforementioned areas (4, 5) are demarcated by ribs of a height less than the thickness of the pieces (7, 8) that will form the upper, which ribs are separated from the surface of the last when the mold is closed; - and in that the channels delimited between opposing edges of consecutive pieces (7, 8) are of a height less than the thickness of the pieces (7, 8) that will form the upper, and said channels widen toward the flesh side of the upper.