An eye testing instrument is disclosed in which accurate aligning and spacing are obtained relative to the human eye to be tested. At least one indication mark is imaged on the cornea or iris of the eye through an objective lens of the instrument and the image of the mark is observed by the inspector. When the image of the mark appears in a predetermined position in the view field, it indicates that the instrument is in a correct position of alignment. Also, the image of the mark appears sharply and clearly whenever an accurate spacing is achieved. Therefore, the necessary adjustment of the testing instrument can be made by moving it relative to the eye backward and forward, up and down and rightward and leftward until a sharp and clear image of the indication mark appears at a predetermined position in the view field.