Provided is an insulating resin material capable of reducing surface roughness of the surface of a cured object, and, when a metal layer is formed on the surface of the cured object, increasing adhesive strength between the cured object and the metal layer.The insulating resin material of the present invention includes a thermosetting resin, a curing agent, a first inorganic filler surface-treated with a first silane coupling agent, and a second inorganic filler surface-treated with a second silane coupling agent. When absolute difference between SP values of a most-abundantly contained thermosetting resin and an organic group of the first silane coupling agent is defined as SP(A), and when absolute difference between SP values of the most-abundantly contained thermosetting resin and an organic group of the second silane coupling agent is defined as SP(B); (SP(A)−SP(B)) is not smaller than 0.5 but not larger than 3.5.