A terminal unit (TU) includes a battery terminal (2) mounted at the leading end of a wiring harness (4), and a holder (8) mounted on the wiring harness (4) at a position distanced from the battery terminal (2). A current sensor (12) is transported separately from the terminal unit (TU) to a connection site to a battery (B). The battery terminal (2) is introduced through the current sensor (12) and the current sensor (12) then is coupled with the holder (8) at the connection site. This operation is performed at a position distanced from the battery (B), and hence can be performed smoothly without being hindered.