An image display apparatus comprising: a light source device including a light source unit (110, 120, 130); a scanning optical system including an image forming unit on which an intermediate image is formed by light from the light source unit (110, 120, 130); and a virtual image optical system configured to guide light of the intermediate image by using a reflecting mirror and a curved transmissive reflection member, wherein the scanning optical system includes an optical scanning unit configured to two-dimensionally scan the light from the light source unit (110, 120, 130) in a main scanning direction defining X direction and a sub-scanning direction defining Y direction orthogonal to the main scanning direction of the image forming unit, the image forming unit is a transmissive member having a concave surface and a convex surface such that the concave surface is curved in a direction in which the light having been deflected by the optical scanning unit is incident on the image forming unit and the convex surface faces the reflecting mirror in an XZ plane formed by the X direction and Z direction defined as a direction orthogonal to both the X direction and the Y direction, and a reflecting surface of the reflecting mirror has a concave surface that is curved in a direction in which light having passed through the image forming unit is incident on the reflecting surface in the XZ plane, characterized in that: the scanning optical system does not include an optical element having a condensing effect or an optical element having a diverging effect between the optical scanning unit and the image forming unit; and the image forming unit is curved in the main scanning direction so as to have a longitudinally-curved cylindrical shape such that the size of the beam spot diameter at each position on the image forming unit varies less than if the image forming unit were flat. a light source device including a light source unit (110, 120, 130); a scanning optical system including an image forming unit on which an intermediate image is formed by light from the light source unit (110, 120, 130); and a virtual image optical system configured to guide light of the intermediate image by using a reflecting mirror and a curved transmissive reflection member, wherein the scanning optical system includes an optical scanning unit configured to two-dimensionally scan the light from the light source unit (110, 120, 130) in a main scanning direction defining X direction and a sub-scanning direction defining Y direction orthogonal to the main scanning direction of the image forming unit, the image forming unit is a transmissive member having a concave surface and a convex surface such that the concave surface is curved in a direction in which the light having been deflected by the optical scanning unit is incident on the image forming unit and the convex surface faces the reflecting mirror in an XZ plane formed by the X direction and Z direction defined as a direction orthogonal to both the X direction and the Y direction, and a reflecting surface of the reflecting mirror has a concave surface that is curved in a direction in which light having passed through the image forming unit is incident on the reflecting surface in the XZ plane, characterized in that: the scanning optical system does not include an optical element having a condensing effect or an optical element having a diverging effect between the optical scanning unit and the image forming unit; and the image forming unit is curved in the main scanning direction so as to have a longitudinally-curved cylindrical shape such that the size of the beam spot diameter at each position on the image forming unit varies less than if the image forming unit were flat. the scanning optical system does not include an optical element having a condensing effect or an optical element having a diverging effect between the optical scanning unit and the image forming unit; and the image forming unit is curved in the main scanning direction so as to have a longitudinally-curved cylindrical shape such that the size of the beam spot diameter at each position on the image forming unit varies less than if the image forming unit were flat.