A battery cell includes: an electrode unit including a positive electrode, a negative electrode, a current collector, and a separator; a housing unit accommodating the electrode unit; a first insulator disposed inside the housing unit and between the electrode unit and the housing unit, an internal terminal disposed inside the housing unit and electrically connected to the current collector; a second insulator disposed inside the housing unit and between the internal terminal and the housing unit; and an external terminal disposed outside the housing unit. A contact surface of the first insulator with the electrode unit has indented shape. The first insulator is fixed to the housing unit.