To provide a lithium ion secondary battery capable of increasing the area of heat radiation, without causing degradation of the accommodation properties.

In the lithium ion secondary battery according to one embodiment of the present invention, a positive electrode capable of storing and discharging lithium, a negative electrode capable of occluding and discharging lithium, and a separator and an electrolyte for ensuring the ion conductivity between the positive and negative electrodes are accommodated inside a battery can, and a foam metal layer is provided on the outer side surface of the battery can.