This electricity storage device comprises an electrode assembly, a case, an electrode terminal and a conductive member. The electrode assembly comprises a positive electrode, a negative electrode and a separator. The separator comprises a first separator part and a second separator part. The separator has a container part that contains portions of the positive electrode other than a tab. The separator has a welded part and a tab facing part. The welded part has facing parts that are positioned on both sides of the tab facing part. The facing parts face the electrode terminal with the conductive member being interposed therebetween. The facing parts are larger in shrinkage amount associated with thermal welding than the other portions of the welded part.