The chemical and the magnetic ordering temperatures in the bcc phase were experimentally determined in the Fe-Co-Al and Fe-Co-Si ternary systems. The equilibrium compositions of these systems were determined by scanning electron microscope and energy dispersive X-ray spectrometer (SEM-EDX) and electron probe microanalyzer (EPMA) after solution treatment at 900-1200^oC, while the transition temperatures were measured by differential scanning calorimetry (DSC). Several vertical section phase diagrams were then constructed and the interaction between the chemical and the magnetic orderings of each binary system was evaluated by extrapolating the ternary data to binary systems. As a result, the effect of the interaction can be summarized as follows: (1) the ferromagnetic state and the B2 ordered configuration stabilize each other in the Fe-Co system, (2) the Curie temperature in the Fe-Al alloys decreases due to the A2/B2/D0₃ ordering, and (3) the Curie temperature in the Fe-Si alloys decreases and increases due to the A2/B2 and the B2/D0₃ orderings, respectively. From the results of the thermodynamic analysis, taking the effects of the interaction into consideration, it was confirmed that the stability of the B2 and the D0₃ configurations and the ferromagnetic state are strongly affected by the interaction effect.