A guide marker includes a substrate and a radio-wave reflecting unit for reflecting radio waves at certain intensity in all directions in a virtual plane, including the incident direction of the radio waves, the radio-wave reflecting unit being provided in the surface of the substrate. The radio-wave reflecting unit includes a concave and convex portions provided in the substrate or radio-wave reflectors which resonate at the frequency of incident radio waves and which reflect the radio waves in the incident direction. The radio-wave reflectors are mounted on the substrate. A visual guide marker device includes one of a light-reflecting component having a reflection characteristic and a light-generating component which self-generates light, and a guide marker including a dielectric material.