In our study, for ion–polymer interaction in gel-type polymer electrolyte (GPE), two kinds of ions were used. GPE systems were composed of Mg or Li salt, organic solvent (γ-BL), and polymer matrix prepared by chemical crosslinking of NBR with poly(ethylene glycol)methylethermethacrylate (PEGMEM) having polar group (CH2 CH2 O) in the side chain of monomer. GPE consisting of Li+ ion had higher ionic conductivity than that of Mg2+ ion at below 100wt.% of electrolyte content (1M salt/γ-BL). On the other hand, GPE consisting of Mg2+ ion had higher ionic conductivity than that consisting of Li+ ion at over 120wt.% of electrolyte content (1M salt/γ-BL). The maximum liquid electrolyte content was 200wt.% for all GPE systems. And the highest ionic conductivity of 3.3 × 10−2 Scm−1 was achieved for the case of Mg2+-GPE with 200wt.% of liquid electrolyte contents at 20°C. The interaction between ionic species and polymer matrix in GPE was investigated by using Fourier transform infrared spectroscopy (FT-IR). Also, cyclic voltammogram of Mg2+-GPE confirmed the electrochemical property of divalent cation with two electron-transfer reactions.