An integrating sphere for a spectrometer, including: an integrating spherical body with a light entrance window for allowing an entry of light emitted from a sample, a first light detection window, and a second light detection window; a first detector attachment section located on the outside of the first light detection window; and a second detector attachment section located on the outside of the second light detection window in such a manner that the detection field of a detector to be attached to the second detector attachment section coincides with the detection field of a detector to be attached to the first detector attachment section.