Abstract: The invention comprises an improved concave supporting and adjusting mechanism for axial flow type combine harvesters wherein a supporting frame for the concave has been provided and which is adjustable in height. The concave supporting frame comprises front and rear cross bars disposed below the front and rear edges, respectively of the concave and has ends of crank arms pivotally attached thereto, the other ends of the crank arms being attached to inner ends of respective stub shafts which shafts extend through the associated side panels and which can be pivoted for adjusting the position of the supporting frame and the concave supported thereon.