A microscope comprising: a pair of Cassegrain reflectors (200, 200A, 200B) that are coaxially installed with a measurement position interposed therebetween, wherein each of the pair of Cassegrain reflectors (200, 200A, 200B) includes a primary mirror and a secondary mirror disposed coaxially with the primary mirror and laterally supported by a plurality of supporting rods, and is configured to reflect light incident from an opening formed on an axial line of the primary mirror by the secondary mirror, reflect the light by the primary mirror, and emit the light to the measurement position from a side of the secondary mirror, wherein at least one of the pair of Cassegrain reflectors (200, 200A, 200B) is retained by a Cassegrain reflector retention mechanism that comprises: a retainer that retains the Cassegrain reflector (200, 200A, 200B); and a rotation adjustment mechanism that adjusts rotational positions of the plurality of supporting rods of the Cassegrain reflector (200, 200A, 200B) retained by the retainer about the axial line; wherein the rotation adjustment mechanism is configured to adjust the rotational positions of the plurality of supporting rods of the Cassegrain reflector (200, 200A, 200B) so that the plurality of supporting rods of the pair of Cassegrain reflectors (200, 200A, 200B) overlap each other when viewed along the axial line. a pair of Cassegrain reflectors (200, 200A, 200B) that are coaxially installed with a measurement position interposed therebetween, wherein each of the pair of Cassegrain reflectors (200, 200A, 200B) includes a primary mirror and a secondary mirror disposed coaxially with the primary mirror and laterally supported by a plurality of supporting rods, and is configured to reflect light incident from an opening formed on an axial line of the primary mirror by the secondary mirror, reflect the light by the primary mirror, and emit the light to the measurement position from a side of the secondary mirror, wherein at least one of the pair of Cassegrain reflectors (200, 200A, 200B) is retained by a Cassegrain reflector retention mechanism that comprises: a retainer that retains the Cassegrain reflector (200, 200A, 200B); and a rotation adjustment mechanism that adjusts rotational positions of the plurality of supporting rods of the Cassegrain reflector (200, 200A, 200B) retained by the retainer about the axial line; wherein the rotation adjustment mechanism is configured to adjust the rotational positions of the plurality of supporting rods of the Cassegrain reflector (200, 200A, 200B) so that the plurality of supporting rods of the pair of Cassegrain reflectors (200, 200A, 200B) overlap each other when viewed along the axial line. a retainer that retains the Cassegrain reflector (200, 200A, 200B); and a rotation adjustment mechanism that adjusts rotational positions of the plurality of supporting rods of the Cassegrain reflector (200, 200A, 200B) retained by the retainer about the axial line; wherein the rotation adjustment mechanism is configured to adjust the rotational positions of the plurality of supporting rods of the Cassegrain reflector (200, 200A, 200B) so that the plurality of supporting rods of the pair of Cassegrain reflectors (200, 200A, 200B) overlap each other when viewed along the axial line.