An object of the present invention is to provide a lithium ion secondary battery enabling improvement of output characteristics at the time of charge and discharge at low temperature and at room temperature. A lithium ion secondary battery according to the present invention for achieving the above object includes a positive electrode plate (11) including a positive electrode mix layer, and a negative electrode plate (12) including a negative electrode mix layer (45). The negative electrode mix layer (45) contains a graphite-type material (42), metal oxide (44), and a conductive assistant (43). The conductive assistant (43) is a carbon material that does not dope or dedope lithium ions, and a mixing ratio of the conductive assistant (43) is 0.4 weight % or more and less than 1.2 weight % of weight of the negative electrode mix layer (45).