Harvesting header for a grain harvesting machine, comprising: - a central header section, - a pair of lateral header sections (15, 17) hinged to the opposite sides (13a, 13b) of the central section and arranged to rotate relative to the central section for assuming a working configuration, in which the three header sections (13, 15, 17) are mutually horizontally aligned, and a rest or transport configuration, in which the lateral header sections (15, 17) overlap the central section, each of said three header sections (13, 15, 17) being provided with: - a support frame (19, 21, 23), wherein the support frame of the central header section can be firmly associated with a grain harvesting machine, and wherein the support frame (21, 23) of each lateral header section (15, 17) is hinged to the support frame of the central section, - a substantially rectilinear motor-driven cutting bar (29, 31, 33) arranged in front of the cutting header and associated with the support frame (19, 21, 23) by means of a hydraulic suspension, wherein the cutting bar (29, 31, 33) comprises a blade having a plurality of substantially trapezoid-shaped knives and capable of carrying out a to-and-fro movement by means of motor-driven control member, - a motor-driven pick-up reel (45, 47, 49) arranged substantially above the cutting bar (29, 31, 33) and supported on the support frame (19, 21, 23) by means of swivel arms associated with hydraulic cylinders, - a transport belt conveyor (37, 39, 41) arranged downstream of the cutting bar (29, 31, 33) and equipped with a draper (53, 55, 57, 59,61) rotatable on rollers, wherein the transport belt (39, 41) of the lateral header sections (15, 17) is configured to feed the material cut by the cutting bar (29, 31, 33) towards the central header section, i.e. in a direction substantially perpendicular to the advance direction of the harvesting header during grain cutting, wherein the transport belt of the central header section comprises a central belt portion and a pair of lateral belt portions (39b, 39c), the lateral belt portions (39b, 39c) being configured to feed the material coming from the adjacent lateral header sections (15, 17) and from the cutting bar of the central header section towards the central belt portion, and the central belt portion being configured to cooperate with a feeding roller provided in the central header section for feeding the material downstream of the harvesting header towards the rear part of the harvesting header. - a central header section, - a pair of lateral header sections (15, 17) hinged to the opposite sides (13a, 13b) of the central section and arranged to rotate relative to the central section for assuming a working configuration, in which the three header sections (13, 15, 17) are mutually horizontally aligned, and a rest or transport configuration, in which the lateral header sections (15, 17) overlap the central section, - a support frame (19, 21, 23), wherein the support frame of the central header section can be firmly associated with a grain harvesting machine, and wherein the support frame (21, 23) of each lateral header section (15, 17) is hinged to the support frame of the central section, - a substantially rectilinear motor-driven cutting bar (29, 31, 33) arranged in front of the cutting header and associated with the support frame (19, 21, 23) by means of a hydraulic suspension, wherein the cutting bar (29, 31, 33) comprises a blade having a plurality of substantially trapezoid-shaped knives and capable of carrying out a to-and-fro movement by means of motor-driven control member, - a motor-driven pick-up reel (45, 47, 49) arranged substantially above the cutting bar (29, 31, 33) and supported on the support frame (19, 21, 23) by means of swivel arms associated with hydraulic cylinders, - a transport belt conveyor (37, 39, 41) arranged downstream of the cutting bar (29, 31, 33) and equipped with a draper (53, 55, 57, 59,61) rotatable on rollers, wherein the transport belt (39, 41) of the lateral header sections (15, 17) is configured to feed the material cut by the cutting bar (29, 31, 33) towards the central header section, i.e. in a direction substantially perpendicular to the advance direction of the harvesting header during grain cutting, wherein the transport belt of the central header section comprises a central belt portion and a pair of lateral belt portions (39b, 39c), the lateral belt portions (39b, 39c) being configured to feed the material coming from the adjacent lateral header sections (15, 17) and from the cutting bar of the central header section towards the central belt portion, and the central belt portion being configured to cooperate with a feeding roller provided in the central header section for feeding the material downstream of the harvesting header towards the rear part of the harvesting header.