A powder for a magnet, the powder being used for a rare-earth magnet, comprising: magnetic particles, constituting the powder for a magnet, each containing a hydride of a rare-earth element in an amount of less than 40% by volume and the balance being an iron-containing material that contains Fe; wherein: a phase of the hydride of the rare-earth element is adjacent to a phase of the iron-containing material, an interval between adjacent phases of the hydride of the rare-earth element with the phase of the iron-containing material provided therebetween is 3 μm or less an antioxidation layer is provided on the surface of each of the magnetic particles, the antioxidation layer having an oxygen permeability coefficient (30°C) of less than 1.0 × 10 -11 m 3 ·mJ(s·m 2 ·Pa), the antioxidation layer having a single-layer configuration consisting of only a low-oxygen-permeability layer composed of a material having an oxygen permeability coefficient (30°C) of less than 1.0 × 10 -11 m 3 ·mJ(s·m 2 ·Pa) or a multilayer configuration in which the low-oxygen-permeability layer and a low-moisture-permeability layer are stacked, the low-moisture-permeability layer composed of a material having a moisture permeability coefficient (30°C) of less than 1000 × 10 -13 kg/(m·s·MPa), chracterised in that: a resin used as the low-oxygen-permeability layer is one selected from polyamide resins, polyester, and polyvinyl chloride. magnetic particles, constituting the powder for a magnet, each containing a hydride of a rare-earth element in an amount of less than 40% by volume and the balance being an iron-containing material that contains Fe; wherein: a phase of the hydride of the rare-earth element is adjacent to a phase of the iron-containing material, an interval between adjacent phases of the hydride of the rare-earth element with the phase of the iron-containing material provided therebetween is 3 μm or less an antioxidation layer is provided on the surface of each of the magnetic particles, the antioxidation layer having an oxygen permeability coefficient (30°C) of less than 1.0 × 10 -11 m 3 ·mJ(s·m 2 ·Pa), the antioxidation layer having a single-layer configuration consisting of only a low-oxygen-permeability layer composed of a material having an oxygen permeability coefficient (30°C) of less than 1.0 × 10 -11 m 3 ·mJ(s·m 2 ·Pa) or a multilayer configuration in which the low-oxygen-permeability layer and a low-moisture-permeability layer are stacked, the low-moisture-permeability layer composed of a material having a moisture permeability coefficient (30°C) of less than 1000 × 10 -13 kg/(m·s·MPa), a phase of the hydride of the rare-earth element is adjacent to a phase of the iron-containing material, an interval between adjacent phases of the hydride of the rare-earth element with the phase of the iron-containing material provided therebetween is 3 μm or less an antioxidation layer is provided on the surface of each of the magnetic particles, the antioxidation layer having an oxygen permeability coefficient (30°C) of less than 1.0 × 10 -11 m 3 ·mJ(s·m 2 ·Pa), the antioxidation layer having a single-layer configuration consisting of only a low-oxygen-permeability layer composed of a material having an oxygen permeability coefficient (30°C) of less than 1.0 × 10 -11 m 3 ·mJ(s·m 2 ·Pa) or a multilayer configuration in which the low-oxygen-permeability layer and a low-moisture-permeability layer are stacked, the low-moisture-permeability layer composed of a material having a moisture permeability coefficient (30°C) of less than 1000 × 10 -13 kg/(m·s·MPa), chracterised in that: a resin used as the low-oxygen-permeability layer is one selected from polyamide resins, polyester, and polyvinyl chloride.