PURPOSE: To eliminate the need to adjust a contact plate even when a core conductor is different in diameter, and to detect securely whether a coating is removed properly or not by arranging two contact plates between side edges on the same plane at an interval.

CONSTITUTION: Two contact plates 3 and 4 made of an elastic conductor plate are installed between side edges on the same plane at an interval 5, and base parts 6 and 7 of the contact plates 3 and 4 are fitted to a slanting part 2 provided to a base 1 with screws 8 and 9. Then, the core conductor (f) after the clad of an electric wire terminal is removed is slid to contact both contact plates 3 and 3 while passed as shown by an arrow, and consequently the core conductor (f) short-circuits both contact plates 3 and 4, so a detecting circuit is closed to display the exposure of the core conductor. If the coating is removed insufficiently and the core conductor (f) is not exposed completely, both contact plates 3 and 4 are not short-circuited, so the exposure is not displayed.