Provided are a seed-coating agent, coated seeds, and a seed-coating method that make it possible for reductions in germination speed to be suppressed for seeds that have been coated with a seed-coating agent that includes elemental iron. This seed-coating agent includes elemental iron and is used to coat the surface of seeds. The seed-coating agent is characterized in that the detected-intensity ratio Fe/FeO for Fe to FeO in an x-ray diffraction of the seed-coating agent is 1.0-12. These coated seeds have a coating layer formed on the surface thereof by means of the seed-coating agent that includes elemental iron. The coated seeds are characterized in that the detected-intensity ratio Fe/FeO for Fe to FeO in an x-ray diffraction of the coating layer is no more than 4.5
