An iron nitride system magnetic powder comprising of particles comprised primarily of Fe16N2 (having an average particle diameter of up to 25 nm, for example) is provided, to which one or more elements selected from Si, P and Ti is adhered. The powder has a C/Fe atomic ratio of 0.5 to 30%, preferably a (Si+P+Ti)/Fe atomic ratio of 0.1 to 10%. With ΔHc defined (Hc0−Hc1)/Hc0×100, the powder has a ΔHc of up to 5%, and with Δσs defined as (σs0−σs1)/σs0×100, a Δσs of up to 20%. The powder can provide an ignition temperature of 140° C. or above, and a tap density of 1.0 g/cm3 or above. Hc0 and σs0 are the coercive force (kA/m) and saturation magnetization (Am2/kg), respectively, of the iron nitride system magnetic powder after adhesion, and Hc1 and σs1 are the coercive force (kA/m) and saturation magnetization (Am2/kg), respectively, of the powder after it has been stored in a thermo-hygrostat for one week at a temperature of 60° C. and a relative humidity of 90%.