A concentration-dependent Curie temperature for amorphous (Fe1-xTMx)1-yBy alloys is given as a solution of a cubic equation using the coherent-potential approximation; and a conclusion has been reached for the exchange inreraction, that JFe-Fe is positive, JTM-TM and JFe-TM are negative. The present conclusion is different from Onodera's result for Fe-Mn-B alloys.