An image display apparatus comprising: a laser light source unit configured to output a luminous flux; a light source driving unit configured to drive the laser light source unit based on image data a scanning mirror unit configured to display said image data on a projection surface by reciprocating the luminous flux in a vertical direction while reciprocating the luminous flux along a going path and a returning path in a horizontal direction, characterized in that the image display apparatus further comprises: an external light sensor for sensing brightness of external light; a light adjustment level setting unit configured to receive a sensor value from the external light sensor, and to determine a light adjustment level for the image data from the received sensor value and a previously stored correspondence table; a bit shift processing unit configured to adjust a luminance value of each pixel included in the image data based on the light adjustment level; and a dimming processing unit configured to bring the adjusted luminance value of every other pixel along the going path to zero and to bring the adjusted luminance value of each or every other pixel of the returning path to zero according to a predetermined rule and based on the light adjustment level, wherein the light source driving unit is configured to increase or decrease a gain of a driving current applied to the laser light source unit based on the light adjustment level. a laser light source unit configured to output a luminous flux; a light source driving unit configured to drive the laser light source unit based on image data a scanning mirror unit configured to display said image data on a projection surface by reciprocating the luminous flux in a vertical direction while reciprocating the luminous flux along a going path and a returning path in a horizontal direction, characterized in that the image display apparatus further comprises: an external light sensor for sensing brightness of external light; a light adjustment level setting unit configured to receive a sensor value from the external light sensor, and to determine a light adjustment level for the image data from the received sensor value and a previously stored correspondence table; a bit shift processing unit configured to adjust a luminance value of each pixel included in the image data based on the light adjustment level; and a dimming processing unit configured to bring the adjusted luminance value of every other pixel along the going path to zero and to bring the adjusted luminance value of each or every other pixel of the returning path to zero according to a predetermined rule and based on the light adjustment level, wherein the light source driving unit is configured to increase or decrease a gain of a driving current applied to the laser light source unit based on the light adjustment level. an external light sensor for sensing brightness of external light; a light adjustment level setting unit configured to receive a sensor value from the external light sensor, and to determine a light adjustment level for the image data from the to receive a sensor value from the external light sensor, and to determine a light adjustment level for the image data from the received sensor value and a previously stored correspondence table; a bit shift processing unit configured to adjust a luminance value of each pixel included in the image data based on the light adjustment level; and a dimming processing unit configured to bring the adjusted luminance value of every other pixel along the going path to zero and to bring the adjusted luminance value of each or every other pixel of the returning path to zero according to a predetermined rule and based on the light adjustment level, wherein the light source driving unit is configured to increase or decrease a gain of a driving current applied to the laser light source unit based on the light adjustment level.