A battery unit comprising: a case accommodating an electrode assembly and having an opening; a cap plate closing the opening, the cap plate having a terminal insertion portion (35, 36); a terminal member (320, 330) extending into the case through the terminal insertion portion (35, 36) from an outside of the case and coupled to the electrode assembly, the terminal member (320, 330) comprising: a current collector (324, 334) electrically coupled to the electrode assembly; a terminal portion (321, 331) extending parallel to an outer surface of the cap plate outside of the case; and a connection portion (325, 335) electrically coupled to the current collector (324, 334) and to the terminal portion (321, 331); and a fixing member (340, 350) in the terminal insertion portion (35, 36) and fixing the terminal member (320, 330) to the cap plate, the fixing member (340, 350) comprising injection-molded plastic resin in the terminal insertion portion (35, 36) and surrounding the terminal member (320, 330), wherein a gap (G1, G2) separates the terminal portion (321, 331) from the outer surface of the cap plate, wherein the terminal portion (321, 331) extends in a first direction (I, III) along the outer surface of the cap plate, wherein the connection portion (325, 335) comprises: a first portion (322, 332) extending in a second direction, which is a thickness direction of the cap plate, from an edge (321a, 331a) of the terminal portion (321, 331), in a third direction (III, I) which is opposite to the first direction (I, III); and a second portion (323, 333) extending in the third direction (III, I) from an edge (322a, 332a) of the first portion (322, 332) in the second direction; and wherein the current collector (324, 334) extends in the second direction from an edge of the second portion (323, 333) in a fourth direction (IV, V), which crosses the first direction (I, III) and the second direction, the edge extending in the third direction (III, I), characterized in that the second portion (323, 333) is entirely embedded in the fixing member (340, 350). a case accommodating an electrode assembly and having an opening; a cap plate closing the opening, the cap plate having a terminal insertion portion (35, 36); a terminal member (320, 330) extending into the case through the terminal insertion portion (35, 36) from an outside of the case and coupled to the electrode assembly, the terminal member (320, 330) comprising: a current collector (324, 334) electrically coupled to the electrode assembly; a terminal portion (321, 331) extending parallel to an outer surface of the cap plate outside of the case; and a connection portion (325, 335) electrically coupled to the current collector (324, 334) and to the terminal portion (321, 331); a current collector (324, 334) electrically coupled to the electrode assembly; a terminal portion (321, 331) extending parallel to an outer surface of the cap plate outside of the case; and a connection portion (325, 335) electrically coupled to the current collector (324, 334) and to the terminal portion (321, 331); and a fixing member (340, 350) in the terminal insertion portion (35, 36) and fixing the terminal member (320, 330) to the cap plate, the fixing member (340, 350) comprising injection-molded plastic resin in the terminal insertion portion (35, 36) and surrounding the terminal member (320, 330), wherein a gap (G1, G2) separates the terminal portion (321, 331) from the outer surface of the cap plate, wherein the terminal portion (321, 331) extends in a first direction (I, III) along the outer surface of the cap plate, wherein the connection portion (325, 335) comprises: a first portion (322, 332) extending in a second direction, which is a thickness direction of the cap plate, from an edge (321a, 331a) of the terminal portion (321, 331), in a third direction (III, I) which is opposite to the first direction (I, III); and a second portion (323, 333) extending in the third direction (III, I) from an edge (322a, 332a) of the first portion (322, 332) in the second direction; and wherein a first portion (322, 332) extending in a second direction, which is a thickness direction of the cap plate, from an edge (321a, 331a) of the terminal portion (321, 331), in a third direction (III, I) which is opposite to the first direction (I, III); and a second portion (323, 333) extending in the third direction (III, I) from an edge (322a, 332a) of the first portion (322, 332) in the second direction; and wherein the current collector (324, 334) extends in the second direction from an edge of the second portion (323, 333) in a fourth direction (IV, V), which crosses the first direction (I, III) and the second direction, the edge extending in the third direction (III, I), characterized in that the second portion (323, 333) is entirely embedded in the fixing member (340, 350).