An active material of silicon, tin or a compound containing silicon or tin is formed on a current collector of a negative electrode in form of a plurality of island regions so that the island regions are separated from one another. Furthermore, a conductive protective film is formed on the current collector so as to cover the island regions. The conductive protective film is formed so as to also cover exposed regions (space portions) of the current collector on which the island regions are not formed. Thus, expansion/shrink of the active region following charge/discharge can be absorbed by the conductive protective film formed in the space portions between the island regions. Also, adhesiveness of the active material with the current collector can be improved.