The parallax barrier type 3D-HUD virtual image display uses binocular disparity to recognize the 3D images, but due to the inconsistency between congestion and adjustment, 3D image sickness is likely to occur due to the relationship between the crosstalk ratio of the 3D virtual image and the amount of parallax. By clarifying the relationship between above factors quantitatively, the conditions for reducing 3D image sickness are calculated.