A head-up display apparatus to be mounted on a vehicle to project an image on a projection member by causing a light of the image to be reflected on the projection member to display a virtual image of the image visible by an occupant, the head-up display apparatus comprising: a projector to project a polarized light of the image; and a light guide portion to guide the light of the image from the projector toward the projection member, wherein an image longitudinal direction (Dil) is defined as a direction along a vertical direction of the vehicle, and an image lateral direction (Dis) is defined as a direction perpendicular to the image longitudinal direction in the image, in a condition where the image is displayed as the virtual image, and a tangential direction of a reflection cross section of the light of the image reflected on the projection member is rotated about a rotation axis, which is in a traveling direction (Dc) of the light of the image, by 90 degrees or less in a first direction with respect to the image longitudinal direction, characterized in that the head-up display apparatus further comprises a polarizing plate located on an optical path between the light guide portion and the projection member and having a transmission axis along which a transmittance of the polarized light becomes maximum, wherein a projection polarization azimuth angle (α0) is defined as an azimuth angle of a polarization direction (Dpp) of the light of the image projected from the projector, and a transmission axis azimuth angle (β) is defined as an azimuth angle of the transmission axis of the polarizing plate, the azimuth angles being relative to the image lateral direction as a reference orientation, the polarizing plate makes the projection polarization azimuth angle different from the transmission axis azimuth angle to tilt the polarization direction of the light of the image reflected on the projection member relative to both of the image longitudinal direction and the image lateral direction, a direction represented by the transmission axis azimuth angle is rotated about the rotation axis by 90 degrees or less in a second direction with respect to a direction represented by the projection polarization azimuth angle, and the first direction and the second direction are opposite to each other. a projector to project a polarized light of the image; and a light guide portion to guide the light of the image from the projector toward the projection member, wherein an image longitudinal direction (Dil) is defined as a direction along a vertical direction of the vehicle, and an image lateral direction (Dis) is defined as a direction perpendicular to the image longitudinal direction in the image, in a condition where the image is displayed as the virtual image, and a tangential direction of a reflection cross section of the light of the image reflected on the projection member is rotated about a rotation axis, which is in a traveling direction (Dc) of the light of the image, by 90 degrees or less in a first direction with respect to the image longitudinal direction, characterized in that the head-up display apparatus further comprises a polarizing plate located on an optical path between the light guide portion and the projection member and having a transmission axis along which a transmittance of the polarized light becomes maximum, wherein a projection polarization azimuth angle (α0) is defined as an azimuth angle of a polarization direction (Dpp) of the light of the image projected from the projector, and a transmission axis azimuth angle (β) is defined as an azimuth angle of the transmission axis of the polarizing plate, the azimuth angles being relative to the image lateral direction as a reference orientation, the polarizing plate makes the projection polarization azimuth angle different from the transmission axis azimuth angle to tilt the polarization direction of the light of the image reflected on the projection member relative to both of the image longitudinal direction and the image lateral direction, a direction represented by the transmission axis azimuth angle is rotated about the rotation axis by 90 degrees or less in a second direction with respect to a direction represented by the projection polarization azimuth angle, and the first direction and the second direction are opposite to each other.