A light amount adjustment device comprising: a base plate including an aperture in one surface thereof for forming a light path; a plurality of light amount adjustment members (31A-31D) including at least a first light amount adjustment member and a second light amount adjustment member adjacent to said first light amount adjustment member in the optical-axis direction, each configured to adjust an amount of light passing through said aperture; and a plurality of driving units (DU1, DU2), wherein said plurality of light amount adjustment members are advanced to and retracted in a direction perpendicular to the optical axis from different positions in an optical-axis direction of the light path with respect to the aperture by said plurality of driving units arranged on the one surface of said base plate, each of said plurality of driving units (DU1, DU2) includes a movement mechanism (4A-4D) including a first movement mechanism and a second movement mechanism, each of the movement mechanisms (4A-4D) includes either a respective motor (41A-41D) and a respective converter (42A-42D) configured to convert an output from the motor (41A-41D) into a linear motion in said direction perpendicular to the optical axis to linearly advance and retract a respective one of said light amount adjustment members with respect to said aperture, wherein each respective converter is a lead screw, or a respective piezoelectric element and a respective driving rod configured to linearly advance and retract the respective one of said light amount adjustment members with respect to said aperture due to an output of the piezoelectric element; at least portions of the driving units (DU1, DU2) oppose each other with the light amount adjustment members (31A-31D) being sandwiched between the driving units; each of the converters and driving rods, respectively, is engaged with an engaging portion of a respective holding member (32A-32D) which holds said respective light amount adjustment member, wherein the converter and driving rod, respectively, of the first movement mechanism is engaged with the engaging portion of the holding member holding the first light amount adjustment member, and the converter and driving rod, respectively, of the second movement mechanism is engaged with the engaging portion of the holding member holding the second light amount adjustment member; wherein each of the engaging portions is arranged on an end portion of said respective holding member towards the respective converter and the respective driving rod, respectively, and in a direction perpendicular to both an advance and retraction direction of said respective light amount adjustment member and the optical axis direction. a base plate including an aperture in one surface thereof for forming a light path; a plurality of light amount adjustment members (31A-31D) including at least a first light amount adjustment member and a second light amount adjustment member adjacent to said first light amount adjustment member in the optical-axis direction, each configured to adjust an amount of light passing through said aperture; and a plurality of driving units (DU1, DU2), wherein said plurality of light amount adjustment members are advanced to and retracted in a direction perpendicular to the optical axis from different positions in an optical-axis direction of the light path with respect to the aperture by said plurality of driving units arranged on the one surface of said base plate, each of said plurality of driving units (DU1, DU2) includes a movement mechanism (4A-4D) including a first movement mechanism and a second movement mechanism, each of the movement mechanisms (4A-4D) includes either a respective motor (41A-41D) and a respective converter (42A-42D) configured to convert an output from the motor (41A-41D) into a linear motion in said direction perpendicular to the optical axis to linearly advance and retract a respective one of said light amount adjustment members with respect to said aperture, wherein each respective converter is a lead screw, or a respective piezoelectric element and a respective driving rod configured to linearly advance and retract the respective one of said light amount adjustment members with respect to said aperture due to an output of the piezoelectric element; at least portions of the driving units (DU1, DU2) oppose each other with the light amount adjustment members (31A-31D) being sandwiched between the driving units; each of the converters and driving rods, respectively, is engaged with an engaging portion of a respective holding member (32A-32D) which holds said respective light amount adjustment member, wherein the converter and driving rod, respectively, of the first movement mechanism is engaged with the engaging portion of the holding member holding the first light amount adjustment member, and the converter and driving rod, respectively, of the second movement mechanism is engaged with the engaging portion of the holding member holding the second light amount adjustment member; wherein each of the engaging portions is arranged on an end portion of said respective holding member towards the respective converter and the respective driving rod, respectively, and in a direction perpendicular to both an advance and retraction direction of said respective light amount adjustment member and the optical axis direction.