The objective of this study is the establishment of a method for inducing the shell opening of Amusium japonicum by injecting a MgCl2 solution into the adductor muscle. The solutions used were made with natural seawater and 0.2 M, 0.4 M, and 0.6 M MgCl2 solutions in the following quantities, 1 ml, 3 ml, and 5 ml, were used, respectively. After the injection, their adductor muscle relaxed and opened. The opening angle of the shells varied from nine to 12 degrees. The molluscs stayed opened even after mechanical stimulation with the following MgCl2 solutions only: 0.4 M (5 ml), 0.6 M (3 ml), and 0.6 M (5 ml). The molluscs required 26 min 49 s, 40 min 29 s, and 39 min 30 s, respectively, to recover from the effects of the injections. The experimental molluscs showed the same conditions as a control individual 24 hours after the injections. In this study, we obtained the result that the most effective method was to inject 5 ml of the 0.4 M MgCl2 solution into the adductor muscle, because it was necessary for us to resume fast shell movement. The injection of MgCl2 solution into the adductor muscle has proved to be a good method to induce the shell opening of a bivalve species like Amusium japonicum.