A modulating device is provided. The modulating device includes multiple modulating elements, multiple pixel circuits, and a compensation circuit. The pixel circuits are electrically connected to the modulating elements correspondingly. The compensation circuit includes a driving unit, a voltage source, and a current source. The driving unit provides a driving signal to the pixel circuits. The voltage source is electrically connected to the driving unit. The voltage source provides a constant voltage to the pixel circuits. The current source is electrically connected to the driving unit. The current source provides a constant current to the pixel circuits.