To provide a space-saving and inexpensive light amount adjustment device that combines a pair of slide aperture blades rectilinearly sliding in an in-plane orthogonal to an optical axis with a pair of pincers-type oscillating blades, and to provide an optical device employing the light amount adjustment device.

The light amount adjustment device includes: a fixture base plate member that includes a first set of first fixture pins in a pair and a second set of first fixture pins in the pair; a first slide aperture blade that includes a pair of a first rectilinear guides into which one of first fixture pins of the first set and one of first fixture pins of the second set are fitted and a second fixture pin; a second slide aperture blade that includes a pair of second rectilinear guides into which the other of the first fixture pins in the first set and the other of the first fixture pins in the second set are fitted and a third fixture pin, and displaces in a reverse direction to the first slide aperture blade; a first set of first oscillating aperture blades that fits to each of first fixture pins in the first set and the second fixture pin, and interlocks with the first slide aperture blade; and a second set of second oscillating aperture blades that fits to each of first fixture pins in the second set and the third fixture pin, and interlocks with the second slide aperture blade.