A circular dichroism (CD) spectrometer includes an alignment mechanism that automatically adjusts the elements thereof at appropriate positions. The spectrometer has a focusing-lens position-and-orientation adjustment mechanism which adjusts the position and the orientation of the detector-side focusing lens. It also has a detector rotation mechanism which adjusts the orientation of the detector. Firstly, a control PC monitors the CD spectrum of D form of optical enantiomers, and the adjustment mechanism adjusts the focusing lens such that the monitored CD spectrum matches the reference spectrum related to the D form. Next, the control PC moniters CD spectrum of L form of optical enantiomers, and the adjustment mechanism adjusts the focusing lens such that the monitored CD spectrum of the D and L forms become symmetrical. And, the rotation mechanism adjusts the orientation of the detector such that the intensity of the detector signal is maximized.