Disclosed is a lithium ion capacitor comprising a positive electrode, a negative electrode, and an aprotic organic solvent solution of a lithium salt as an electrolyte solution. The positive electrode active material is a substance which can be reversibly doped with lithium ions and/or anions; and the negative electrode active material is a substance which can be reversibly doped with lithium ions. The negative electrode and/or the positive electrode is doped with lithium ions in advance so that the positive electrode potential after short-circuiting the positive electrode and the negative electrode is not more than 2.0 V. When the capacitance per unit weight of the positive electrode is represented by C+(F/g), the weight of the positive electrode active material is represented by W+(g), the capacitance per unit weight of the negative electrode is represented by C-(F/g) and the weight of the negative electrode active material is represented by W-(g), the value of (C- * W-)/(C+ * W+) is not less than 5.