A fuel supply system for a fuel injection device including a fuel injection unit and a holding-and-supplying unit holding the fuel injection unit, the fuel injection unit including a first fuel injection member, a first atomizing mechanism surrounding the first fuel injection member, a second fuel injection member disposed radially outside the first atomizing mechanism, a second atomizing mechanism disposed radially outside the second fuel injection member, and an outer casing surrounding the second atomizing mechanism, wherein: the first atomizing mechanism has an annular air passage defined by the outer circumference of the first fuel injection member and the inner circumference of the second fuel injection member, and an air swirling mechanism disposed between the first fuel injection member and the second fuel injection member; the second atomizing mechanism has an annular air passage defined by the outer circumference of the second fuel injection member and the inner circumference of the outer casing, and an air swirling mechanism disposed between the second fuel injection member and the outer casing; whereby fuel can be atomized and mixed with the combustion air flowing through the annular air passages (41,61) by means of the atomizing mechanisms (40,60), each of the annular air passages (41,61) having an annular air inlet at an upstream end of the annular air passage; characterised in that: the holding-and-supplying unit includes a fuel feed arm supporting the fuel injection unit without covering the annular air inlet of each of the annular air passages; the holding-and-supplying unit is internally provided with a first fuel supply passage through which fuel is supplied to the first fuel injection member and a second fuel supply passage through which fuel is supplied to the second fuel injection member; the holding-and-supplying unit includes an integral assembly of an outer ring joined to the outer casing, an inner ring joined to the second fuel injection member, a central cylindrical part joined to the first fuel injection member, the said fuel feed arm joined to the outer ring, and a combining structure which has an upper connecting part connecting the inner ring to an upper part of the outer ring, a central connecting part connecting the inner ring and the central cylindrical part, and a lower connecting part connecting the inner ring to a lower part of the outer ring; and the air passages are formed between the outer ring and the inner ring and between the inner ring and the cylindrical part. the first atomizing mechanism has an annular air passage defined by the outer circumference of the first fuel injection member and the inner circumference of the second fuel injection member, and an air swirling mechanism disposed between the first fuel injection member and the second fuel injection member; the second atomizing mechanism has an annular air passage defined by the outer circumference of the second fuel injection member and the inner circumference of the outer casing, and an air swirling mechanism disposed between the second fuel injection member and the outer casing; whereby fuel can be atomized and mixed with the combustion air flowing through the annular air passages (41,61) by means of the atomizing mechanisms (40,60), each of the annular air passages (41,61) having an annular air inlet at an upstream end of the annular air passage; characterised in that: the holding-and-supplying unit includes a fuel feed arm supporting the fuel injection unit without covering the annular air inlet of each of the annular air passages; the holding-and-supplying unit is internally provided with a first fuel supply passage through which fuel is supplied to the first fuel injection member and a second fuel supply passage through which fuel is supplied to the second fuel injection member; the holding-and-supplying unit includes an integral assembly of an outer ring joined to the outer casing, an inner ring joined to the second fuel injection member, a central cylindrical part joined to the first fuel injection member, the said fuel feed arm joined to the outer ring, and a combining structure which has an upper connecting part connecting the inner ring to an upper part of the outer ring, a central connecting part connecting the inner ring and the central cylindrical part, and a lower connecting part connecting the inner ring to a lower part of the outer ring; and the air passages are formed between the outer ring and the inner ring and between the inner ring and the cylindrical part. the holding-and-supplying unit includes a fuel feed arm supporting the fuel injection unit without covering the annular air inlet of each of the annular air passages; the holding-and-supplying unit is internally provided with a first fuel supply passage through which fuel is supplied to the first fuel injection member and a second fuel supply passage through which fuel is supplied to the second fuel injection member; the holding-and-supplying unit includes an integral assembly of an outer ring joined to the outer casing, an inner ring joined to the second fuel injection member, a central cylindrical part joined to the first fuel injection member, the said fuel feed arm joined to the outer ring, and a combining structure which has an upper connecting part connecting the inner ring to an upper part of the outer ring, a central connecting part connecting the inner ring and the central cylindrical part, and a lower connecting part connecting the inner ring to a lower part of the outer ring; and the air passages are formed between the outer ring and the inner ring and between the inner ring and the cylindrical part.