Electric storage device, and vehicle-mounted electric storage system

Provided is an electric storage device provided with: a positive electrode including a positive electrode substrate and a positive electrode mixture layer, the positive electrode mixture layer being formed on the positive electrode substrate and containing a positive electrode active material; a negative electrode including a negative electrode substrate and a negative electrode mixture layer, the negative electrode mixture layer being formed on the negative electrode substrate and containing a negative electrode active material; and a separator disposed between the positive electrode and the negative electrode. In the electric storage device, the separator yields a triple value of standard deviation of local air resistance, as measured within a 5-mm diameter circle, of at least 20 seconds/10 cc but not more than 350 seconds/10 cc.