An optical apparatus having a light amount adjustment device capable of realizing a high-speed operation and a high-resolution operation. The light amount adjustment device includes a second motor that has a rotor provided with magnetized poles whose number is two times the number of magnetized poles provided in a rotor of a first motor, so that the second motor has a resolution two times higher than that of the first motor. A control unit of the optical apparatus controls the drives of the first and second motors independently of each other. In a high-speed drive mode, the first and second motors are driven simultaneously or only the first motor is driven. In a low-speed drive mode, only the second motor is driven.