PURPOSE: To dispense with a resistance meter for discriminating an insulation fault between patterns from a fault due to a short circuit, by providing additionally a group of resistors connected in series and a switch element switching over the resistors in the group, between a probe coming into contact with a pattern and a capacitance meter.

CONSTITUTION: A group 4 of resistors is connected in series between a probe 6 coming into contact with a metal wiring pattern 9 on a board 7 to be measured, and a capacitance meter 1. In addition, a switch division 5 selecting one of the resistors in the group 4 is provided. When inspection of the pattern 9 is conducted, a short-circuit wire 10 is selected by the switch division 5 and an electrostatic capacity between the pattern 9 and a reference potential plane 8 is measured. In the case when a measured value thus obtained is within the range of an allowable error of a theoretical value, the capacity is determined to be good, and when the measured value is smaller than the theoretical value, it is determined to be a fault due to a disconnection in the middle of the pattern. In the case when the measured value is larger than the theoretical value, one of the resistors in the group 4 is selected and inserted between the capacitance meter 1 and the probe 6. When a composite resistance found in this state is large sufficiently, it is determined as a fault due to a short circuit between patterns, while it is determined as an insulation fault when the resistance is small.