To improve measurement accuracy of a test device, which does not contact a material when it is gently guided.

This guide device can be used as an inlet or outlet nozzle in a test device to carry out a nondestructive material test by eddy current, and is especially used for linearly guiding an extended object such as a wire. The guide device is built in a guide sleeve and has a brush which is formed so as to function as a damping device 35 to damp the vibration of the passing object. Thereby a wire guided by the guide device so as to protect its surface receives little or no vibration in the crossing direction when it enters the vicinity of a test probe, so that the disturbance can be reduced to increase the accuracy of measurement.