According to the present invention, there are provided a resin composition containing a surface-modified inorganic substance, which is obtained by performing surface modification on an inorganic nitride or an inorganic oxide by using a boronic acid compound, and an epoxy compound, a thermally conductive material including a cured substance of the resin composition, and a device including the thermally conductive material. The boronic acid compound has, for example, an amino group, a thiol group, a hydroxyl group, an isocyanate group, a carboxyl group, or a carboxylic acid anhydride group. By using the resin composition of the present invention, it is possible to provide a thermally conductive material having excellent thermal conductivity and a device having high durability.