An image display apparatus includes a light source device, a light source control unit which controls power supplied to the light source device and an image light emission unit which, utilizing a source light emitted from the light source device, emits an image light. A light quantity measurement unit measures a quantity of the source light. A power/light quantity characteristic derivation unit derives a power/light quantity characteristic. A light quantity adjustment unit, based on the power/light quantity characteristic, adjusts the quantity of the source light or the image light. The light source control unit controls the supplied power to gradually change the light quantity of the source light. The light quantity measurement unit measures the light quantity of the gradually changing source light and acquires light quantity data. The power/light quantity characteristic derivation unit, based on the light quantity data and the supplied power, derives the power/light quantity characteristic.