Mirror unit

A mirror unit comprising:

• a reflecting mirror;
• and
• a holder which holds the reflecting mirror from a back surface thereof,
• the mirror unit rotating about an axis as the holder is pressed by a slider which moves linearly, and being provided in a head-up display device, wherein
• the holder comprises:
• a part to be pressed, which is at a position deviated from a center of the reflecting mirror toward a first end of the reflecting mirror in a direction in which the axis extends, and is pressed by the slider;
• a first support part, which is at a position corresponding to the part to be pressed, and is fixed to the back surface;
• and
• a second support part, which is located closer to a second end opposite to the first end of the reflecting mirror than the first support part, is larger than the first support part in outer shape, and is fixed to the back surface,
• the first support part is fixed to the back surface by a first double-sided tape,
• the second support part is fixed to the back surface by a second double-sided tape,
• the second double-sided tape is formed in a shape of a frame having an opening, and
• an area of the first double-sided tape is less than or equal to an area of the opening.