completely obstructed by the dielectric layer 5 a flow of electric shock current into the cfrp 12 can be completely prevented and damage to the cfrp 12 due to the electric shock current can be completely prevented furthermore according to the fastener 30 of the present embodiment since electric shock current does not flow towards the fastener main body 4 a di dielectric insulator conventionally required between the structural member 11 and the collar 17 for preventing sparks and an insulating rubber cap conventionally attached to cover the whole of the top end section of the male screw section 2 a and the collar 17 attached to prevent a streamer that secondarily discharges electricity from the collar 17 can both be eliminated and the weight of an aircraft can be significantly reduced a fourth embodiment according to the present invention is described using to fig5 a fastener 40 in the present embodiment differs from the above described third embodiment in that a conductive layer 21 is provided instead of the conductive layer 6 described above in which a circumference section positioned to the outside of the through holes 6 a in a radial direction is bent towards made to face the fastener main body 4 side downside in fig5 other components are identical with those in the third embodiment described above and descriptions for these identical components are omitted here moreover the same reference symbols are given to members that are identical with those in the third embodiment according to the fastener 40 of the present embodiment in the case.