An iron-based rare-earth-containing nanocomposite magnet which is an iron-based rare-earth-containing nanocomposite magnet containing an Nd2Fe14B phase and an α-Fe phase and having a composition represented by the empirical formula T100-x-y-z-n(B1-qCq)xRyTizMn (wherein T is at least one transition metal element indispensably including iron and selected from the group consisting of Fe, Co, and Ni; R is at least one rare earth element substantially containing neither La nor Ce; and M is one or more metal elements selected from the group consisting of Al, Si, V, Cr, Mn, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, and Pb), the proportions x, y, z, n, and q satisfying the relationships 4≤x≤10 at.%, 6≤y≤10 at.%, 0.05≤z≤5 at.%, 0≤n≤10 at.%, and 0.05≤q≤0.5, respectively. In the magnet, the content of the α-Fe phase having an average crystal grain diameter of 1-50 nm is 5-60 vol.%, and the content of the Nd2Fe14B phase having an average crystal grain diameter of 5-100 nm is 40-90 vol.%. A nonmagnetic phase containing at least Ti and C (carbon) is present at grain boundaries between the α-Fe phase and the Nd2Fe14B phase.