A sensing apparatus includes a prism, a metal film provided on a surface of the prism, a substrate that is provided on a surface of the prism and which has formed therein a channel for supplying a sample to the metal film, a light source for issuing light, an optical unit for incident light by which the light being issued from the light source is launched into the prism at such an angle that the light is totally reflected on a boundary surface between the prism and the metal film, the optical unit for incident light including a light intensity distribution adjusting section that reduces difference between the maximum and the minimum values in the intensity distribution of the light that is launched into the prism, and a light detecting unit for detecting the light that is generated in neighborhood of the metal film.