To provide a support device for display adjustment capable of exactly and quickly displaying the irregularity of a brightness.

A photodiode 11 outputs an output waveform which exhibits the brightness of a liquid crystal display monitor. A sensor amplifier 12 amplifies the output waveform and supplies the amplified waveform to a full-wave rectifying circuit 13. An integrator 14 integrates the full-wave-rectified output waveform every half cycle. Therein, the integrator 14 performs the integration every half cycle while resetting an integration value in accordance with a timing pulse supplied from a timing control circuit 16. An S/H circuit 15 samples and holds the integration value every half cycle by means of the integrator 14. An analog voltmeter 17 displays the integration value held by the S/H circuit 15 every half cycle. An adjustment person rotates a volume of a common voltage while referring the voltage display and performs the adjustment of the brightness.