The spectroscopy module is provided with a body portion for transmitting light, a spectroscopic portion for dispersing light made incident from the front plane of the body portion into the body portion to reflect the light on the front plane, a light detecting element having a light detecting portion for detecting the light dispersed and reflected by the spectroscopic portion and electrically connected to a wiring formed on the front plane of the body portion by face-down bonding, and an underfill material filled in the body portion side of the light detecting element to transmit the light. The light detecting element is provided with a light-passing hole through which the light advancing into the spectroscopic portion passes, and a reservoir portion is formed on a rear plane of the body portion side in the light detecting element so as to enclose a light outgoing opening of the light-passing hole.