The present invention relates to a method for producing transformed earthworms using the gonad-regenerating capability of earthworms, to transformed earthworms produced by the method, and to a method for producing recombinant proteins from the body fluids of transformed earthworms. The method for producing transformed earthworms according to the present invention is a novel biotechnology technique which overcomes the drawbacks of conventional transgenesis techniques, and which has high injection efficiency. The method for producing transformed earthworms according to the present invention uses regenerative blast cells having totipotency, such as embryonic stem cells, and therefore, recombinant genes can be incorporated throughout the entire transformant, and recombinant proteins can be made from the body fluids of the transformant. The method of the present invention injects a target gene directly into a gonad, thus eliminating the need of a surrogate (animal), and uses a fertile transformant, thus continuously producing a plurality of transformants. The method of the present invention is simpler than conventional transgenesis techniques, and does not require expensive equipment or expertise.