a plurality of secondary battery cells;

a housing member accommodating the plurality of the secondary battery cells therein; and

an insulating member disposed on an inner surface of the housing member, preventing flow of electrical current to the housing member, having a heat transfer function to discharge heat of the secondary battery cell externally, and formed to have a predetermined thickness,

wherein the housing member comprises:

a cooling plate member which forms a bottom of the housing member; and

a sidewall member which forms a side portion of the housing member,

wherein the insulating member comprises:

a bottom insulating portion disposed on the cooling plate member; and

a sidewall insulating portion disposed on the sidewall member,

wherein the bottom insulating portion and the sidewall insulating portion meet at two edges of the bottom insulating portion,

wherein the bottom insulating portion is configured to have a first predetermined thickness and the sidewall insulating portion is configured to have a second predetermined thickness, and

wherein the bottom insulating portion is configured to have a flat shape and the sidewall insulating portion is configured to have a flat shape.