A battery module, comprising: a plurality of battery cells (100; 103, 104), each having an electrode assembly, a case for accommodating the electrode assembly, and an electrode lead composed of a positive electrode lead and a negative electrode lead connected to the electrode assembly and exposed out of the case, wherein the positive electrode lead and the negative electrode lead are exposed at same side of the case; and a connection member configured to electrically connect the battery cells, wherein the plurality of battery cells are classified into a first battery group having battery cells disposed side by side in a first direction and a second battery group having battery cells disposed side by side in the first direction so that electrode leads of the battery cells thereof face electrode leads of the battery cells of the first battery group, wherein the connection member is located between the first battery group and the second battery group, wherein the electrode leads of the battery cells are connected to the connection member, respectively, wherein an electrode lead of any one battery cell of the first battery group is in contact with any one of an upper surface and a lower surface of the connection member, wherein an electrode lead of a battery cell of the second battery group, which is located to face the any one battery cell of the first battery group, is in contact with the other one of the upper surface and the lower surface of the connection member, and wherein at least the positive electrode lead and the negative electrode lead of any one battery cell of the first battery group are located so that a partial region of surfaces thereof faces the positive electrode lead and the negative electrode lead of one of the battery cells of the second battery group, based on the connection member. a plurality of battery cells (100; 103, 104), each having an electrode assembly, a case for accommodating the electrode assembly, and an electrode lead composed of a positive electrode lead and a negative electrode lead connected to the electrode assembly and exposed out of the case, wherein the positive electrode lead and the negative electrode lead are exposed at same side of the case; and a connection member configured to electrically connect the battery cells, wherein the plurality of battery cells are classified into a first battery group having battery cells disposed side by side in a first direction and a second battery group having battery cells disposed side by side in the first direction so that electrode leads of the battery cells thereof face electrode leads of the battery cells of the first battery group, wherein the connection member is located between the first battery group and the second battery group, wherein the electrode leads of the battery cells are connected to the connection member, respectively, wherein an electrode lead of any one battery cell of the first battery group is in contact with any one of an upper surface and a lower surface of the connection member, wherein an electrode lead of a battery cell of the second battery group, which is located to face the any one battery cell of the first battery group, is in contact with the other one of the upper surface and the lower surface of the connection member, and wherein at least the positive electrode lead and the negative electrode lead of any one battery cell of the first battery group are located so that a partial region of surfaces thereof faces the positive electrode lead and the negative electrode lead of one of the battery cells of the second battery group, based on the connection member.