Battery with secure short-circuiting mechanism

A battery includes: a battery element having a cathode and an anode; a package can containing the battery element and being electrically connected to one of the cathode and the anode; and external connection terminal being connected to the other one of the cathode and the anode; and having a plate-like base contained in the package can and a leading portion extending to outside of the package can; and an insulating member separating the external connection terminal from the battery element. The base of the external connection terminal is spaced from an internal wall face of the package can, and the insulating member has notches at a position where the base of the external connection terminal is layered on the insulating member in the thickness direction of the package can.