To maintain a reaching path to the spinal cord located in the body for the treatment of the nerve of fish which maintains the freshness by breaking the spinal cord, without spoiling appearance of fish and appearance in cooked fish, and without needing muscular strength from absence of bone treatment.

A tube 18 provided with a bending 9 is used, and a wire made of a shape memory alloy is inserted to the front end portion 12 of the spinal cord, in a manner of going through an inner portion 3 of the conjunctiva which is a blind spot normally in the orbit 2, passing through a space 6 between the eye 4 and the skull 5, passing apertures of the skull 8 locating on the front portion of the brain and linked to the neural arch 7 of the spinal cord, and reaching to the front end portion 12 of the spinal cord 11 using the bending 9 so that the front end portion 10 faces to the spinal cord 11 direction. The reaching path to the spinal cord 11 is maintained by an inside hole 13 of the tube 18 with bending 9.