A head-up display for a vehicle capable of detecting a distance between the vehicle and another vehicle in front of the vehicle, comprising: a mirror unit comprising a first mirror for reflecting first and second image lights toward a windshield of the vehicle; wherein the mirror unit comprises: an image generator configured to emit light linearly-polarized in a first direction, and light linearly-polarized in a second direction orthogonal to the first direction; a second mirror disposed to be separated from the first mirror so as to transmit the light linearly-polarized in the first direction, and reflect the light linearly-polarized in the second direction to the first mirror; a third mirror disposed to be separated from the second mirror so as to reflect the light linearly-polarized in the first direction that has transmitted through the second mirror to the first mirror; a first rotation mechanism configured to change the inclination of the first mirror, a second rotation portion configured to change an inclination of the second mirror; and a third rotation portion configured to change an inclination of the third mirror, a display layer located at the windshield of the vehicle to display a first virtual image corresponding to the first image light in a first region, and display a second virtual image corresponding to the second image light in a second region; and a controller configured to change an inclination of the first mirror and the third mirror to change display positions of the first and the second virtual image, wherein the controller changes the display positions of the first virtual image and the second virtual image according to the distance between the vehicle and another vehicle in front of the vehicle, wherein the controller changes the inclination of the first mirror and the third mirror to allow the first virtual image and the second virtual image to overlap with each other. a mirror unit comprising a first mirror for reflecting first and second image lights toward a windshield of the vehicle; wherein the mirror unit comprises: an image generator configured to emit light linearly-polarized in a first direction, and light linearly-polarized in a second direction orthogonal to the first direction; a second mirror disposed to be separated from the first mirror so as to transmit the light linearly-polarized in the first direction, and reflect the light linearly-polarized in the second direction to the first mirror; a third mirror disposed to be separated from the second mirror so as to reflect the light linearly-polarized in the first direction that has transmitted through the second mirror to the first mirror; a first rotation mechanism configured to change the inclination of the first mirror, a second rotation portion configured to change an inclination of the second mirror; and a third rotation portion configured to change an inclination of the third mirror, a display layer located at the windshield of the vehicle to display a first virtual image corresponding to the first image light in a first region, and display a second virtual image corresponding to the second image light in a second region; and a controller configured to change an inclination of the first mirror and the third mirror to change display positions of the first and the second virtual image, wherein the controller changes the display positions of the first virtual image and the second virtual image according to the distance between the vehicle and another vehicle in front of the vehicle, wherein the controller changes the inclination of the first mirror and the third mirror to allow the first virtual image and the second virtual image to overlap with each other. an image generator configured to emit light linearly-polarized in a first direction, and light linearly-polarized in a second direction orthogonal to the first direction; a second mirror disposed to be separated from the first mirror so as to transmit the light linearly-polarized in the first direction, and reflect the light linearly-polarized in the second direction to the first mirror; a third mirror disposed to be separated from the second mirror so as to reflect the light linearly-polarized in the first direction that has transmitted through the second mirror to the first mirror; a first rotation mechanism configured to change the inclination of the first mirror, a second rotation portion configured to change an inclination of the second mirror; and a third rotation portion configured to change an inclination of the third mirror, a display layer located at the windshield of the vehicle to display a first virtual image corresponding to the first image light in a first region, and display a second virtual image corresponding to the second image light in a second region; and a controller configured to change an inclination of the first mirror and the third mirror to change display positions of the first and the second virtual image, wherein the controller changes the display positions of the first virtual image and the second virtual image according to the distance between the vehicle and another vehicle in front of the vehicle, wherein the controller changes the inclination of the first mirror and the third mirror to allow the first virtual image and the second virtual image to overlap with each other.