A thermosetting resin composition that is capable of suppressing the occurrence of gaps that form between an adherend and a sheet even when the sheet is closely adhered by pressing against an adherend having a roughened surface with a low pressing force. The thermosetting resin composition includes an epoxy resin as a main component resin and boron nitride agglomerated particles as an inorganic filler. A proportion of the boron nitride agglomerated particles in the resin composition is 40% by volume or more and 50% by volume or less, and a proportion of the inorganic filler other than the boron nitride agglomerated particles in the resin composition is 7% by volume or less.