PURPOSE: To prevent generation of the ghost of a variable vertex prism.

CONSTITUTION: This variable vertex prism is constituted by covering the circumference of two sheets of glass plates 11, 13 facing each other with bellows 17, hermetically sealing liquid therein and relatively tilting two sheets of the glass plates 11, 13 facing each other, thereby varying the vertex formed by two sheets of the glass plates 11, 13. The contact surfaces of two sheets of the glass plates 11, 13 to liquid are subjected to antireflection coating. The generation of the ghost, etc., is prevented even in the case of a high-illuminance subject, such as illumination lamp. The generation of the ghost occurring in color smear, etc., is lessened even if this device is used for a lens having a long focal length at a telephoto end for the purpose of preventing image blurring.