A motorcycle brake disc rotor being an annular body comprising: at least two layers, rigidly connected to each other, wherein each layer is a one-piece part made separately and has a radially external lateral surface and a radially internal lateral surface, opposite annular friction surfaces, internal cooling through channels for cooling the rotor, formed in at least one of the at least two layers, extending from the radially external lateral surface to the radially internal lateral surface so as to direct air flow substantially in a radial direction and having a length defined by a distance between said lateral surfaces, the annular friction surfaces forming at least partially, outward facing sides of the annual body outer layers, and inward facing sides of the annular body outer layers having regions directly contacting the adjacent layer and regions free from contact with the adjacent layer, said outer layers regions directly contacting the adjacent layer serve for said rigid connection of the layers, and each of the internal through cooling channels is, at least partially, formed by a region of one outer layer, which is free from contact with the adjacent layer, and a region of the other outer layer, which is free from contact with the adjacent layer, said internal through cooling channels made with variable cross-section, with a width thereof increasing from the radially internal lateral surface to the radially external lateral surface, characterized in that the width of the internal cooling channels is substantially the same within a rotor working area and increases within 2 to 3 mm from the radially external lateral surface by up to 1.5 mm per 1 mm of a distance from the radially external lateral surface. at least two layers, rigidly connected to each other, wherein each layer is a one-piece part made separately and has a radially external lateral surface and a radially internal lateral surface, opposite annular friction surfaces, internal cooling through channels for cooling the rotor, formed in at least one of the at least two layers, extending from the radially external lateral surface to the radially internal lateral surface so as to direct air flow substantially in a radial direction and having a length defined by a distance between said lateral surfaces, the annular friction surfaces forming at least partially, outward facing sides of the annual body outer layers, and inward facing sides of the annular body outer layers having regions directly contacting the adjacent layer and regions free from contact with the adjacent layer, said outer layers regions directly contacting the adjacent layer serve for said rigid connection of the layers, and each of the internal through cooling channels is, at least partially, formed by a region of one outer layer, which is free from contact with the adjacent layer, and a region of the other outer layer, which is free from contact with the adjacent layer, said internal through cooling channels made with variable cross-section, with a width thereof increasing from the radially internal lateral surface to the radially external lateral surface, characterized in that the width of the internal cooling channels is substantially the same within a rotor working area and increases within 2 to 3 mm from the radially external lateral surface by up to 1.5 mm per 1 mm of a distance from the radially external lateral surface.