A steel rib straightening machine for construction comprises a bottom plate, a cylinder device, a supporting plate device, a positioning device, a moving device and a fixed device. A first supporting rod, a first support, a second support, a third support, a first transverse rod and a second supporting rod are arranged on the bottom plate. The cylinder device comprises a first cylinder, a push rod, a push block and a first spring. The supporting plate device comprises a first supporting plate, a second supporting plate, a second spring and a first positioning rod. The positioning device comprises a first fixing block, a second fixing block, a positioning frame, a third fixing block, a screw and a fourth fixing block. The moving device comprises a moving frame, a moving block, a third spring, a fourth spring and a fifth spring. The fixed device comprises a second cylinder, a first vertical rod, a first fixed frame, a supporting block, a second fixed frame, a third fixed frame, a fourth fixed frame, a second transverse rod, a third transverse rod and an ejecting block. The steel rib straightening machine can be used for quickly straightening steel ribs, and straightening is convenient and stable.