A method of producing a transgenic silkworm that spins bagworm silks and producing a large quantity of bagworm silks by transgenic technology is developed and provided. A gene encoding a modified bagworm Fib H and a transgenic silkworm in which the gene is introduced, wherein the gene is obtained by cloning a gene fragment encoding a bagworm Fib H-like polypeptide comprising a partial amino acid sequence of bagworm Fib H, and fusing the gene fragment to a gene fragment encoding silkworm-derived Fib H, are provided.
