Stereoscopic display device and circularly polarized light glasses

A stereoscopic display device (100) is provided with: a first image display unit (110) that outputs linearly polarized first image light (151); a second image display unit (120) that outputs linearly polarized second image light (152); a first phase difference plate (112) that modulates the first image light (151) output from the first image display unit (110) and converts the modulated first image light into first elliptically polarized light; a second phase difference plate (122) that modulates second image light (152) output from the second image display unit (120) and converts the modulated second image light into second elliptically polarized light that rotates in the same direction as the rotation direction of the first elliptically polarized light; and a half mirror (130) that transmits the first elliptically polarized light and turns the first elliptically polarized light into first circularly polarized light that rotates in the same direction as the rotation direction of the first elliptically polari