An optical apparatus comprising: a first rotatable reflecting member including a first plane reflecting surface and a second plane reflecting surface; a first optical system configured to sequentially reflect along a first optical path, by a plurality of plane reflecting surfaces (14-1, 14-2, 14-3, 14-4) included therein, light reflected by the first reflecting surface of the first reflecting member an even number of times and cause the light to be incident on the second reflecting surface of the first reflecting member; a first adjusting device configured to change a rotation angle of the first reflecting member to translate an optical path of light that is reflected by and exits the second reflecting surface of the first reflecting member; a second rotatable reflecting member including a first plane reflecting surface on which the light, that is reflected by and exits the second reflecting surface of the first reflecting member, is incident, and a second plane reflecting surface; a second optical system configured to sequentially reflect along a second optical path, by a plurality of plane reflecting surfaces (16-1, 16-2, 16-3, 16-4) included therein, the light reflected by the first reflecting surface of the second reflecting member an even number of times and cause the light to be incident on the second plane reflecting surface of the second reflecting member; and a second adjusting device configured to change a rotation angle of the second reflecting member to translate an optical path of light that is reflected by and exits the second reflecting surface of the second reflecting member, wherein a rotation axis of the first reflecting member and a rotation axis of the second reflecting member are not parallel with each other, characterized in that the apparatus is configured such that a plane formed and surrounded by the first optical path in the first optical system and a plane formed and surrounded by the second optical path in the second optical system intersect with each other. a first rotatable reflecting member including a first plane reflecting surface and a second plane reflecting surface; a first optical system configured to sequentially reflect along a first optical path, by a plurality of plane reflecting surfaces (14-1, 14-2, 14-3, 14-4) included therein, light reflected by the first reflecting surface of the first reflecting member an even number of times and cause the light to be incident on the second reflecting surface of the first reflecting member; a first adjusting device configured to change a rotation angle of the first reflecting member to translate an optical path of light that is reflected by and exits the second reflecting surface of the first reflecting member; a second rotatable reflecting member including a first plane reflecting surface on which the light, that is reflected by and exits the second reflecting surface of the first reflecting member, is incident, and a second plane reflecting surface; a second optical system configured to sequentially reflect along a second optical path, by a plurality of plane reflecting surfaces (16-1, 16-2, 16-3, 16-4) included therein, the light reflected by the first reflecting surface of the second reflecting member an even number of times and cause the light to be incident on the second plane reflecting surface of the second reflecting member; and a second adjusting device configured to change a rotation angle of the second reflecting member to translate an optical path of light that is reflected by and exits the second reflecting surface of the second reflecting member, wherein a rotation axis of the first reflecting member and a rotation axis of the second reflecting member are not parallel with each other, characterized in that the apparatus is configured such that a plane formed and surrounded by the first optical path in the first optical system and a plane formed and surrounded by the second optical path in the second optical system intersect with each other.