Laser interference device

A laser interference device comprising:

• a measurement mirror being movable in a length measuring direction;
• a reference mirror disposed at a position different from a position of the measurement mirror in an orthogonal direction relative to the length measuring direction;
• a beam splitter having a splitting surface that divides a laser beam outputted from a laser into a measurement light and a reference light;
• a first light guide configured to guide the measurement light incident from the beam splitter and emit the measurement light toward the measurement mirror in the length measuring direction;
• and
• a second light guide configured to guide the reference light incident from the beam splitter and emit the reference light toward the reference mirror in the length measuring direction, wherein
• a first distribution path that is a path of the measurement light from the splitting surface to a light emission surface of the first light guide and a second distribution path that is a path of the reference light from the splitting surface to a light emission surface of the second light guide are mutually equal in a mechanical path length and an optical path length, and
• wherein a group of a plurality of optical elements forming the first light guide and a group of a plurality of optical elements forming the second light guide are mutually the same in a number, a material, and a size of the optical elements.