PURPOSE: To surely collect signal data of a control circuit which are supplied to the main circuit of an electric car, in easy and efficient ways by mounting a substrate module and a buffer module substrate for signal measurement on a control unit.

CONSTITUTION: Signals required to be measured when a model test and a running test are made for the electric car 8, can be easily collected to the test circuit from the control circuit 1 for the electric car 8 in such a manner that only the buffer module substrate 5 for signal measurement is inserted to a slot member for substrate insertion corresponding to a connector for signal measurement, to connect to that connector. The circuit 1 is not influenced by the substrate 5 because the resistance value of a load resistor 11 or a pull-out resistor is made to be high, which is provided for the purpose of preventing from the breakdown of circuit elements caused by static electricity inputted from the outside, and also the signal received in the substrate 5 is outputted to a measuring instrument through an insulation processing part. Invasion of noise generated in the measurement system can be prevented accordingly.