In the spectrometer 1, a lens portion 3 having a spherical surface 35 on which a spectroscopic portion 4 is provided and a bottom plane 31 in which a light detecting element 5 is disposed, has a side plane 32 substantially perpendicular to the bottom plane 31 and a side plane 34 substantially perpendicular to the bottom plane 31 and the side plane 32. Then, a package 11 that houses a spectroscopy module 10 has side planes 16 and 18 respectively coming into planar-contact with the side planes 32 and 34, and contact portions 22 coming into contact with the spherical surface 35. Therefore, the side planes 32 and 34 of the lens portion 3 are respectively brought into planar-contact with the side planes 16 and 18 of the package 11 while bringing the spherical surface 35 of the lens portion 3 into contact with the contact portions 22 of the package 11, that positions the spectroscopic portion 4 and the light detecting element 5 with respect to a light incident window plate 25 of the package 11.