A header for an agricultural machine includes a middle section disposed on a main frame and two side sections adjacent the middle section, a flexible knife bar extending across the width of the header and a conveying device behind the knife bar and designed at the side sections as an endless belt disposed adjacent to the middle section for transporting crop cut by the knife bar laterally. The side sections have supporting arms pivotably disposed on the main frame to support the knife bar of a side section and are rigidly connected to the knife bar. Each supporting arm is connected to the main frame permitting swivelling about a first rotational axis in the vertical direction and about a second rotational axis extending perpendicular to the first.