A wide variety of ionic liquids was prepared by the neutralization of five kinds of imidazole derivatives and nine kinds of acids. Their physical and chemical properties such as melting points, glass transition temperature, viscosity, and ionic conductivity were studied. Among these, imidazoles neutralized with imide-type acids were revealed to have lower melting points and lower glass transition temperature than others. These characteristics a:re quite effective to provide higher ionic conductivity. Especially, N-methylimidazole neutralized with bis(trifluoromethanesulfonyl)imide acid showed 7.23 x 10(-3) S cm(-1) at 25 degreesC. This neutralization method is quite convenient and effective to provide excellent ionic liquid as well as to design suitable models for quaternized onium-type salts.