RECTANGULAR ELECTRICITY STORAGE DEVICE

There is provided a prismatic power storage device having a reduced weight and ensuring a space for an electrode body that expands during charging, while the rigidity of an insulating sheet is ensured. A prismatic power storage device according to an aspect of the present disclosure includes: an electrode body () including a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate; an insulating holder () formed by shaping an insulating sheet () into a box shape and accommodating the electrode body (); a prismatic outer case having an opening and accommodating the electrode body () and the insulating holder (); and a sealing body sealing the opening of the outer case. The insulating sheet () includes a porous body.