To provide a lithium ion secondary cell that can obtain an inexpensive and good cell property even heated in a manufacturing process or mixed with a very small amount of moisture.

In a lithium ion secondary cell including a carbon material for occluding a lithium ion into a negative electrode and using a non-aqueous system electrolyte or a solid type of electrolyte, in the non-aqueous system electrolyte or the solid electrolyte is included in the mixed salt of LiClO4 and LiBF4 (however, the mole ratio of the LiClO4 is 0.98-0.70).