The invention relates to a fastening device for implant device, the fastening device comprising at least two fastening sections, where a first fastening section is arranged with a through hole, a second fastening section is arranged with a protruding part, and where said protruding part is in place in said through hole in a fastening device locking state, where the protruding part on the second fastening section is arranged with a through channel having an inlet and an outlet, said through channel being arranged to receive an implant device feed member, said inlet and outlet being accessible from the exterior of the fastening device in said fastening device locking state, wherein the first fastening section is securely locked to the second fastening section when, in said fastening device locking state, said implant device feed member is in place in the through channel and protrudes from both the inlet and the outlet of said through channel. The invention further relates to an implant device comprising a fastening device, and a method for securely locking a first fastening section of a fastening device for an implant device to a second section of a fastening device for an implant device.