Abstract: An electric circuit apparatus of an injection molding machine includes a connector board which comprises a plurality of connection terminals to which connection wires can be connected, and a plurality of wiring lines each divided into two line segments in order to enable an additional circuit element to be connected to an existing circuit element provided as a standard element. The line segments of each wiring line are electrically connected to a pair of connection terminals. A connection element for short-circuiting or an additional circuit element is selectively connected to the pair of connection terminals.