To provide a lithium ion polymer battery improved in the reliability of a connecting part between a collector and an electrode lead.

A positive electrode and a negative electrode respectively prepared by forming an active material layer on the collector are stacked through a gel electrolyte, the positive electrode 2 comprises an electrode element wherein electrode leads 8 are respectively led out from the active material layer 2a and the positive electrode collector 2b, and the electrode lead has a cut on a part free from the active material layer of the collector to be bent, so that it is composed of the bent part. The negative electrode also has the similar constitution.