The present invention relates to a surface plasmon resonance sensor which has a first dielectric layer, a metal layer disposed on the first dielectric layer, and a second dielectric layer covering the metal layer. The surface plasmon resonance sensor includes: a sensor main body provided with an opening for exposing a part of a surface of the metal layer on a side facing the second dielectric layer, and for allowing a measurement sample to be brought into contact with this surface; a light source for introducing a beam into the metal layer from one end of the metal layer in a longitudinal direction of the metal layer; and a detection unit detecting a beam emitted from the other end of the metal layer, has high sensitivity in measurement, is downsized, and is usable in a simple manner.