Abstract: An apparatus for efficiently observing protein crystals for use in X-ray analysis is provided. This apparatus includes an ultra-compact proximity imaging unit and a three-dimensional observation adaptor (4) attached thereto. The imaging unit includes a CCD camera (2) and a lens system (3) and an illumination system in front of the CCD camera (2). The lens system (3) includes a variable or fixed magnification lens. The three-dimensional observation adaptor (4) has an optical-axis reflective surface (4c) disposed between the frontmost lens of the lens system (3) and a production container (100) containing protein crystals in the optical axis a of the lens system (3) and a revolving reflective surface (4d) disposed opposite the optical-axis reflective surface (4c) revolvably about the optical axis to three-dimensionally observe the crystals contained in the production container (100) in an oblique or lateral direction.