Provided is an electrode stack formed by integrating a first separator, a first electrode plate, a second separator, and a second electrode plate. The first separator has a first separator body, and a first bonding layer that is formed on a principal surface of the first separator body and contains first polyethylene particles. The second separator has a second separator body, and a second bonding layer that is formed on a principal surface of the second separator body and contains second polyethylene particles. The number of particles of the first polyethylene particles per unit area of the first bonding layer is larger than the number of particles of the second polyethylene particles per unit area of the second bonding layer.