The present invention discloses a localized plasmon resonance sensing device and a fiber optic structure. The device comprises an optical fiber and a noble metal nanoparticle layer. The optical fiber has a plurality of notches, and such notches are located on the side surface of the optical fiber. The noble metal nanoparticle layer is located at the notch. As a result, when a light is launched into the optical fiber, a detecting unit can be used to detect a localized plasmon resonance signal which is generated by the interaction between the noble metal nanoparticle layer and the light.