A sensor chip includes: a substrate that has a planar portion; and a diffraction grating on the planar portion and having a metal surface, the diffraction grating having a target substance thereon and including: a plurality of first protrusions periodically arranged in a period equal to or greater than 100 nm and equal to or less than 1000 nm in a first direction parallel to the planar portion, a plurality of base portions located between two adjacent first protrusions and configures a base of the substrate, a plurality of second protrusions formed on upper faces of the plurality of first protrusions, and a plurality of third protrusions formed on the plurality of base portions.