PURPOSE: To eliminate dies by respectively covering both straight sections of a bus bar on both sides of the line connecting the inner and outer corners of the bent section of the bus bar in a plane including the bent section with heat shrinkable liner insulating tubes and winding an insulating tape around the bent section near the tubes.

CONSTITUTION: A bus bar 10 is formed in an L shape as a whole by cutting off the end sections of two linear conductors 12 having rectangular cross sections along 45° oblique lines and butt welding the cut faces of the conductors 12 to each other. Insulating tubes 14 are respectively put on the conductors at the bent section by bringing the end sections 16 of the tubes 14 nearer to each other so that the bus bar 10 cannot be exposed. Then the bus bar 10 is insulated by winding an insulating tape 18 around the bent section along the oblique line connecting the inner corner 20 and outer corner 22 of the bent section. The tube 14 is formed in a pipe-like state by using thermoplastic synthetic resin, such as polyvinyl chloride. Therefore, the bent sections of bus bars having different sizes can be easily and surely insulated without using any die.