PURPOSE: To improve examination accuracy by providing an open collector type driver on a side of an input pattern of a carbon contact type switch and by switching.

CONSTITUTION: A membrane switch 1 to be examined is first set on a setting jig 2, a key housing 5 is further mounted on it, and the switch is connected to a main examining device 3 by connection cords 4a,4b. A level changeover switch 17 of a receiver 14 is switched to an 'H' level in this state. An open collector type driver 13 is provided on a side of an input pattern of the carbon contact type switch and switched, and also output voltage derived to its output pattern is compared with a plurality of comparison reference levels of comparison means 15, 16, whereby not only whether or not switch resistance is good at the time of turning ON and OFF the switch but also insulation resistance between the input and output patterns or with other patterns can be checked.