PURPOSE: To provide a busbar partition plate which is easy to assemble and can meet the change of the conductor sizes of horizontal busbars easily while the function as the busbar partition plate is not sacrificed.

CONSTITUTION: A busbar partition plate 27 has holes 27a through which horizontal busburs 29 are installed and each hole has a plurality of slits 27b in its circumference. Or, the busbar partition plate having the holes through which the horizontal busbars are installed is made of shape-memory resin so as to have gaps between the circumferences of the holes and the horizontal busbars before currents are applied to the horizontal busbars and to make he circumferences of the holes adhere to the horizontal busbars closely by the heat when the currents are applied to the horizontal busbars.