PURPOSE: To enable the confirmation for the testing direction, by using a side viewing mirror which can move to the direct viewing position and a gauge having the functions of both a level and a magnetic needle.

CONSTITUTION: A connector 7 is attached at the tip of an objective part of an endoscope 6 containing an objective lens 1, an eyepiece 3 and an optical fiber 4. A side viewing mirror 5 is coupled to an aperture part 10 in the connector 7 via a cylinder 8 and a shaft 9. A lever 11 is adhered to the cylinder 8, and a wire 13 is bonded at the tip of the lever 11. The wire 13 is connected to a slider 17 provided at the eyepiece of the endoscope. A direction standard unit 22 having the functions of both a level and a magnetic pole is fitted into the tip part of the connector 7. Then the mirror 5 is shifted to a direct viewing position 21 by operating the slider 17. Thus the unit 22 is observed to understand the testing direction.