PROBLEM TO BE SOLVED: To provide an Fe-based alloy composition having a nano dispersion structure and capable of exhibiting excellent magnetic property than conventional, a molding member containing the Fe-based alloy composition, a dust core containing the molding member, an electronic component having the duct core and an electronic device having the electronic component, a magnetic sheet containing the Fe-based alloy composition, a communication component having the magnetic sheet and a communication device having the communication component.SOLUTION: There is provided a Fe-based alloy composition containing 6 atom% to 10 atom% of P, 6 atom% to 8 atom% of C, 2 atom% to 6 atom% of B, 0.4 atom% to 1 atom% of Cu, 1 atom% to 3 atom% of Si and over 0 atom% and 2 atom% or less of Cr and the balance Fe with inevitable impurities, and containing a crystal having a crystal particle diameter calculated by a Scherrer formula based on diffraction peaks derived from boc-Fe around 2&thetas;=100° in X ray diffraction sp
