Poly(ethylene oxide)alpha,omega-dicarboxylic acid alkali metal salts were prepared as inherently ion-conductive salts. Since the average molecular weight of the poly(ethylene oxide) matrix is about 300, the salts are totally amorphous and show ionic conductivity of 10(-4)-10(-6) S cm(-1) at 50 degrees C. An upwardly convex curve was seen in the Arrhenius plots of the ionic conductivity, reflecting the diffusion of ions in a viscous matrix. Under the same condition, the salts with larger cation showed higher ionic conductivity. These salts, except lithium salt, were miscible with polyether oligomers at any composition, maintaining the high ionic conductivity.