To provide a thermosetting resin composition excellent in curability and storage stability and a semiconductor device using the same.

This resin composition contains (A) a compound having at least two epoxy groups, (B) a compound having at least two phenolic hydroxyl groups, (C) a quaternary-nitrogen-containing cure accelerator, and (D) an inorganic filler. The cure accelerator is represented by formula (1) (wherein R1, R2, R3, and R4 are each H or an aryl, alkyl or aralkyl group provided at least two of R1-R4 may combine with each other to form a cyclic structure; X is a compound having at least three hydroxyl or carboxyl groups; X- is an anion formed by releasing a proton from X; Xn is a complex comprising n X's; and n is an integer or decimal fraction larger than 0).