To provide a distribution board having bus bars of low Joule's heat exhibiting good heat dissipation effect in which standardization can be simplified, assembling workability is enhanced, and alteration in the rated current of a circuit breaker is compatible with easily.

A planar bus bar 11 and bus bars 12A, 12B, 12C and 12D having a L-shaped cross-section are coupled by means of screws to form H-shape, the L-shaped bus bars 12A and 12C are secured to a common insulated bar 13 by means of screws and then the insulated bar 13 is secured to the crosspiece 15 of the frame of a generator panel 1 through an insulation block 14. A coupling bar 10 is connected with the L-shaped bus bars 12B and 12D by means of screws and a longitudinal bus bar group 8 is connected with the upper terminal 3a of a circuit breaker.