Immune-inducible antimicrobial peptides were produced using transgenic silkworms that expressed Rel family transcription factor, truncated BmRelish1 (BmRelish1t) genes under the control of the BmA3 promoter using the piggyBac vector. BmRelish1t gene contains all domains of Bmrelish: a Rel homolog domain (RHD), nuclear localization signal (NLS), acidic and hydrophobic amino acids (AHAA) rich region except the Ankyrin repeat domain (ANK) and the death domain (DD). (1:1) Mixtures of the donor vector (pG-3xP3EGFP-BmA3BmRelish1t) and helper vector were micro-injected into 1,800 eggs of bivoltin silkworms, Baegokjam and EGFP-induced fluorescence was observed for 25 broods of transgenic silkworms under a florescence stereomicroscope. Analysis by real-time PCR indicated that transgenic silkworms expressing BmRelish1t recombinant proteins displayed higher mRNA expression levels of the Bombyx mori antimicrobial peptides such as lebocin, moricin, and nuecin than the normal silkworms. Moreover, transgenic silkworms expressing BmRelish1t showed antibacterial activity against Escherichia coli. We suggest that transgenic expression of BmRelish1t may find useful applications for the production of various antimicrobial peptides at the same time in transgenic silkworms.