In a state that the body portion 4 is regulated by inner wall planes 27, 29, 28 of the package 3 so as not to move in parallel or perpendicularly with respect to the rear plane 4b, the spectroscopic module is directly supported by the package 3, thereby when the spectrometer is downsized, the spectroscopic module 2 can be supported securely and also there is provided securely a positional accuracy between the light incident opening 22a of the package 3, the spectroscopic portion 6 of the spectroscopic module 2 and the light detecting element 7. Further, the lead 23 is buried into the package 3 to give derivation and support by the lead deriving portion 26, thereby the lead deriving portion 26 in itself of the package 3 is allowed to act as a base when wire bonding is conducted to electrically connect the lead 23 with the light detecting element 7, thus preventing breakage and deviation of the spectroscopic module 2.