A battery pack comprising: a plurality of battery blocks including a plurality of battery cells arranged at fixed positions, the plurality of battery cells being connected together by a plurality of lead plates, each of the plurality of battery cells welded to a respective welded part in one-to-one correspondence and each welded part being connected to a first end of one lead plate; and a circuit board to which the plurality of battery blocks are fixed, wherein each of the plurality of battery blocks have terminal parts to be connected to the circuit board at the same position, the circuit board has connection parts, one of connection parts being connected to a corresponding one of the terminal parts of the each of the plurality of battery blocks to connect by coupling the terminal parts of the each of the plurality of battery blocks to the connection parts of the circuit board in one-to-one correspondence, the plurality of battery blocks in series or in parallel, and the plurality of battery blocks are coupled via the circuit board, characterized in that the plurality of battery blocks are aligned, end to end, along a long axis of the battery cells, and the plurality of battery cells in each battery block are arranged at fixed positions by a holder, said holder comprising a first holder and second holder, coupled via the plurality of battery cells, a first end of the plurality of battery cells inserted in the first holder and a second end of the plurality of battery cells inserted in the second holder, with opposing surfaces of the first and second holders configured as a fitting structure, and both holders being coupled to the circuit board, thereby held in a mutually coupled state. a plurality of battery blocks including a plurality of battery cells arranged at fixed positions, the plurality of battery cells being connected together by a plurality of lead plates, each of the plurality of battery cells welded to a respective welded part in one-to-one correspondence and each welded part being connected to a first end of one lead plate; and a circuit board to which the plurality of battery blocks are fixed, wherein each of the plurality of battery blocks have terminal parts to be connected to the circuit board at the same position, the circuit board has connection parts, one of connection parts being connected to a corresponding one of the terminal parts of the each of the plurality of battery blocks to connect by coupling the terminal parts of the each of the plurality of battery blocks to the connection parts of the circuit board in one-to-one correspondence, the plurality of battery blocks in series or in parallel, and the plurality of battery blocks are coupled via the circuit board, characterized in that the plurality of battery blocks are aligned, end to end, along a long axis of the battery cells, and the plurality of battery cells in each battery block are arranged at fixed positions by a holder, said holder comprising a first holder and second holder, coupled via the plurality of battery cells, a first end of the plurality of battery cells inserted in the first holder and a second end of the plurality of battery cells inserted in the second holder, with opposing surfaces of the first and second holders configured as a fitting structure, and both holders being coupled to the circuit board, thereby held in a mutually coupled state.