To provide a sharper marker by suppressing the generation of heat when forming the marker with which a desired form or size hardly disappears at a desired position while securing imaging function by X-rays, or the like.

A guidewire 1 has a linear core 2, a resin layer 3 covering a core body part 22 of the core 2, and an imaging part 4 formed to cover a top of the core 2. The resin layer 3 is added with a color coupler which is colored by radiating laser light, and a contrast agent composed of powder of a metal oxide. The imaging part 4 is added with a contrast agent composed of metal powder in a resin and presents a high imaging function from the resin layer 3. On an outer surface 30 of the resin layer 3, a helical visible marker is formed, for example. The visible marker is formed by coloring the color coupler by irradiating a front surface of the resin layer 3 with laser light.