Provided is a spectroscope that can be manufactured easily, can be reduced in size, and can provide high wavelength resolution of a specific spectral band. Specifically, provided is a spectroscope with a diffraction grating 331 that deflects and separates incident light in different directions depending on to an element of the incident light, at least one optical element 332a, diffusing a light that has passed through this diffraction grating 331 and has entered the optical element 332a, a line sensor 333, which receives the light that has passed through the optical element 332a, thereby only light that has a specific deflection angle within a specific range of wavelengths from among all the light that entered said optical element 332a is selectively expanded and received.