In an optical member coupling apparatus for coupling an exchangeable lens unit and an optical member such as a color-separating prism with each other, a supporting section for movably supporting the optical member in a plane perpendicular to the optical axis is provided, whereby even when the optical axes of the lens unit and optical member deviate from each other, they can be adjusted easily. A color-separating prism 2 is attached, together with a lens unit 1, to a panel 3 by means of first and second bases 7 and 8 which are respectively movable only along X and Y axes in a plane perpendicular to the optical axis. The first and second bases 7 and 8 respectively have elliptical holes 7G and 8G into which a joystick 16 can be inserted. When the optical axis of the lens unit deviates from the imaging center of a CCD attached to the color-separating prism 2, screws 10A to 11B are unfastened, and the joystick 16 is inserted through the tool-inserting holes 7G and 8G and is wrenched so that the color-separating prism 2 is moved in a plane perpendicular to the optical axis.