A projector that includes a discharge tube and is adapted to project an image by using a light source including the discharge tube, the projector comprising: a discharge tube drive section that is adapted to supply the discharge tube with electric power; and an electric power control section that is adapted to control the level of the electric power with which the discharge tube drive section supplies the discharge tube to perform a normal mode in which the discharge tube drive section supplies electric power of a rated electric power level and a power saving mode in which the discharge tube drive section supplies electric power of a power saving level lower than the rated electric power level when the image is not required to be projected, wherein the power saving mode is a mode in which slight light emission can be maintained; characterized in that: the electric power control section is adapted to set the level of the electric power supplied to the discharge tube at a single low luminance level (N') lower than the rated electric power level but higher than the power saving level, and when the normal mode is changed to the power saving mode, the electric power control section is adapted to change the level of electric power supplied to the discharge tube at a first speed from the rated electric power level to the single low luminance level but change the level of electric power supplied to the discharge tube at a second speed slower than the first speed from the single low luminance level to the power saving level; and wherein the electric power control section is adapted to set the level of the electric power supplied to the discharge tube at a single intermediate level lower than the rated electric power level but higher than the power saving level, and when the power saving mode is changed to the normal mode, the electric power control section is adapted to change the level of electric power supplied to the discharge tube at a third speed from the power saving level to the single intermediate level but change the level of electric power supplied to the discharge tube at a fourth speed slower than the third speed from the single intermediate level to the rated electric power level. a discharge tube drive section that is adapted to supply the discharge tube with electric power; and an electric power control section that is adapted to control the level of the electric power with which the discharge tube drive section supplies the discharge tube to perform a normal mode in which the discharge tube drive section supplies electric power of a rated electric power level and a power saving mode in which the discharge tube drive section supplies electric power of a power saving level lower than the rated electric power level when the image is not required to be projected, wherein the power saving mode is a mode in which slight light emission can be maintained; characterized in that: the electric power control section is adapted to set the level of the electric power supplied to the discharge tube at a single low luminance level (N') lower than the rated electric power level but higher than the power saving level, and when the normal mode is changed to the power saving mode, the electric power control section is adapted to change the level of electric power supplied to the discharge tube at a first speed from the rated electric power level to the single low luminance level but change the level of electric power supplied to the discharge tube at a second speed slower than the first speed from the single low luminance level to the power saving level; and wherein the electric power control section is adapted to set the level of the electric power supplied to the discharge tube at a single intermediate level lower than the rated electric power level but higher than the power saving level, and when the power saving mode is changed to the normal mode, the electric power control section is adapted to change the level of electric power supplied to the discharge tube at a third speed from the power saving level to the single intermediate level but change the level of electric power supplied to the discharge tube at a fourth speed slower than the third speed from the single intermediate level to the rated electric power level. the electric power control section is adapted to set the level of the electric power supplied to the discharge tube at a single low luminance level (N') lower than the rated electric power level but higher than the power saving level, and when the normal mode is changed to the power saving mode, the electric power control section is adapted to change the level of electric power supplied to the discharge tube at a first speed from the rated electric power level to the single low luminance level but change the level of electric power supplied to the discharge tube at a second speed slower than the first speed from the single low luminance level to the power saving level; and wherein the electric power control section is adapted to set the level of the electric power supplied to the discharge tube at a single intermediate level lower than the rated electric power level but higher than the power saving level, and when the power saving mode is changed to the normal mode, the electric power control section is adapted to change the level of electric power supplied to the discharge tube at a third speed from the power saving level to the single intermediate level but change the level of electric power supplied to the discharge tube at a fourth speed slower than the third speed from the single intermediate level to the rated electric power level.