A battery module comprising: a battery cell stack configured to have a structure in which a plurality of battery cells or unit modules connected to each other in series and/or in parallel is stacked in a state in which each of the battery cells or the unit modules is stood on one side thereof; voltage sensing members (122, 124) provided with connecting terminals electrically connected to electrode terminal connection parts (118, 119) of the battery cells located at a front and a rear of the battery cell stack for detecting voltages of the battery cells or the unit modules; an upper case configured to have a structure for covering an end of one side of the battery cell stack and portions of upper and lower ends of the battery cell stack, the upper case being provided with mounting parts, into which the voltage sensing members (122, 124) are inserted and mounted; and a lower case configured to have a structure that is coupled to the upper case while covering an end of the other side of the battery cell stack and portions of the upper and lower ends of the battery cell stack, the lower case being provided at a front thereof with external input and output terminals, wherein each of the voltage sensing members (122, 124) is configured to have a receptacle structure in which each of the voltage sensing members (122, 124) is fitted onto a corresponding one of the electrode terminal connection parts (118, 119) from an upper part of each of the voltage sensing members (122, 124), and each of the mounting parts is configured to have a structure in which the width of the mounting part is decreased in a direction in which a corresponding one of the electrode terminal connection parts (118, 119) is inserted, characterized in that each of the connecting terminals comprises two or more connection pieces elastically connected to opposite sides of a corresponding one of the electrode terminal connection parts (118, 119), the connection pieces are configured to have a structure in which a distance between the connection pieces is decreased such that the connection pieces come into tight contact with the opposite sides of a corresponding one of the electrode terminal connection parts (118, 119) as a corresponding one of the electrode terminal connection parts (118, 119) is inserted into the connection pieces. a battery cell stack configured to have a structure in which a plurality of battery cells or unit modules connected to each other in series and/or in parallel is stacked in a state in which each of the battery cells or the unit modules is stood on one side thereof; voltage sensing members (122, 124) provided with connecting terminals electrically connected to electrode terminal connection parts (118, 119) of the battery cells located at a front and a rear of the battery cell stack for detecting voltages of the battery cells or the unit modules; an upper case configured to have a structure for covering an end of one side of the battery cell stack and portions of upper and lower ends of the battery cell stack, the upper case being provided with mounting parts, into which the voltage sensing members (122, 124) are inserted and mounted; and a lower case configured to have a structure that is coupled to the upper case while covering an end of the other side of the battery cell stack and portions of the upper and lower ends of the battery cell stack, the lower case being provided at a front thereof with external input and output terminals, wherein each of the voltage sensing members (122, 124) is configured to have a receptacle structure in which each of the voltage sensing members (122, 124) is fitted onto a corresponding one of the electrode terminal connection parts (118, 119) from an upper part of each of the voltage sensing members (122, 124), and each of the mounting parts is configured to have a structure in which the width of the mounting part is decreased in a direction in which a corresponding one of the electrode terminal connection parts (118, 119) is inserted, characterized in that