A binder for an electrode of a lithium secondary battery contains a water dispersion of a polyurethane. The polyurethane has been formed of (A) a polyisocyanate, (B) a compound having two or more active hydrogen groups, (C) a compound having one or more active hydrogen groups and a hydrophilic group, and (D) a chain extending agent. The (B) compound having two or more active hydrogen groups contains an olefinic polyol and/or a carbonate diol having a carbon number between carbonate bond chains of less than 6. The binder has high adhesiveness to a collector, does not cause release in press molding, has high flexibility, and is excellent in bindability and resistance to an electrolytic solution.