Optical unit for vehicle lighting device

An optical unit (10) used in a vehicle lighting device (210), includes a plurality of first shades (12A) which are disposed adjacent to each other in a vehicle width direction and are separated by a specific gap, wherein at least one of the first shades (12A) is movable between an advanced position which blocks a part of light emitted from a light source (14) and a retreated position which does not block the light, a second shade (12B), which is engaged with an end portion in the vehicle width direction of the at least one of the first shades, and driven by the first shade (12A) to move between the advanced position and the retreated position, and covers the gap between the adjacent first shades (12A), and a movement mechanism (18) which is connected to the at least one first shade (12A) and moves the first shade (12A) to one of the advanced position and the retreated position.