Circular dichroism can be accurately measured even when a phase modulation element with a distortion component is used.;A circular dichroism measuring method using a circular dichroism measuring device 2 includes a step of measuring Ip(t) (S101: phase amount change acquisition step), a step of measuring Is(t) (S102: sample data acquisition step), a step of converting Ip(t) to δ(t) (S103: phase amount change acquisition step), a step of converting Is(t) to Is(δ) (S104: analysis step/Is(δ) calculation step), and a step of performing curve fitting to calculate matrix elements S00, S02, and S03 (S105: analysis step/matrix element calculation step).
