Provided is a lithium ion capacitor that can retain a capacity under a high temperature environment and has small increase in internal resistance while using an aqueous binder for a positive electrode. A lithium ion capacitor includes: a positive electrode; a negative electrode; and an electrolytic solution contacting the positive electrode and the negative electrode. The electrolytic solution includes an organic solvent and a lithium salt electrolyte having an imide structure; the positive electrode includes a collector foil and a positive electrode active material; and the positive electrode active material is held onto the collector foil through a binder including a polymer having a RED value to the electrolytic solution of more than 1, the RED value representing a relative energy difference with respect to the electrolytic solution based on Hansen solubility parameters.