Thermosetting resin composition, thermosetting resin composition for fiber-reinforced composite material, prepreg using the same, and honeycomb sandwich panel

Disclosed is a thermosetting resin composition with superior toughness. The thermosetting resin composition comprises a thermosetting resin and an adsorbing filler in which a thermoplastic resin (C) has been adsorbed into a filler, and satisfies an adsorption coefficient in the range of higher than 0 to 0.8 that is defined below (formula 1). (Formula 1) adsorption coefficient = amount of aforementioned thermoplastic resin (C) (parts by mass) adsorbed in 100 parts by mass of aforementioned filler / specific gravity of aforementioned thermoplastic resin (C) / DBP oil absorption (mL/100g) of aforementioned filler