An amorphous iron-based alloy which comprises not more than 25 atom % of Si and 2.5 to 25 atom % of B (providing that the sum of Si and B falls in the range of 15 to 35 atom %), 1.5 to 20 atom % of Cr, 0.2 to 10 atom % of either or both of P and C, and the balance to make up 100 atom % substantially of Fe excels in fatigue property. An amorphous iron-based alloy which contains not more than 30 atom % of at least one element selected from the group consisting of Co, Ni, Ta, Nb, Mo, W, V, Mn, Ti, Al, Cu and Zr in addition to the components making up the aforementioned alloy excels in amorphous texture of forming ability and fatigue property. Since these alloys are also excellent in tensile strength at fracture, thermal resistance, corrosionproofness, and electromagnetic property, they prove highly useful as electromagnetic materials and as reinforcements in various industrial materials.