Positive electrode active material for lithium ion electric storage device, and lithium ion electric storage device using the same

[Problem] The present invention aims to enhance a characteristic of a lithium ion electric storage device upon charging or discharging with high load, and increasing a working temperature range thereof. [Means for Solving Problem] In a positive electrode active material used for a lithium ion electric storage device, the BET specific surface area is 1500 m 2 /g or more and 3000 m 2 /g or less, the ratio A of the pore volume within the range of the pore diameter of 0.6 nm or more and less than 1 nm to the pore volume within the range of the pore diameter of 0.6 nm or more and 200 nm or less in the active material satisfies 0≦A≦0.80, and the ratio B of the active material of the pore volume within the range of the pore diameter of 1 nm or more and 6 nm or less to the pore volume within the range of the pore diameter of 0.6 nm or more and 200 nm or less in the active material satisfies 0.20≦B≦1.0. By virtue of this structure, the lithium ion electric storage device can be provided that is excellent in the charging/discharging characteristic when it is given a high load, and that can satisfactorily operate even under an environment of −30° C.