A vehicle lighting fixture comprising: a housing having an opening; an outer lens configured to form a lighting chamber together with the housing by being attached to the housing so as to close the opening of the housing; a light source configured to include a light emitting device; a mounting substrate configured to allow the light source to be mounted thereon; a reflector configured to reflect light emitted from the light source; and an extension, wherein: the light source, the mounting substrate, the reflector, and the extension are housed in the lighting chamber; the light source, the reflector, the extension, and the outer lens constitute an optical system; the vehicle lighting fixture further comprises a substrate holder arranged in an upper half portion of the lighting chamber, the mounting substrate being attached to the substrate holder to hold the mounting substrate; the reflector is arranged in a lower half portion of the lighting chamber below the mounting substrate; the extension is arranged in front of the substrate holder and the reflector; the outer lens is positioned in front of the extension; the extension includes a window hole portion positioned in front of the reflector, an upper extension portion configured to extend from an upper edge portion of the window hole portion upward, and an annular flange portion configured to extend from respective outer rim portions of the window hole portion and the upper extension portion rearward; the reflector is configured to receive the light emitted from the light source and reflect the light so that the light can pass through the window hole portion and the outer lens to be projected outward; the flange portion of the extension is configured to receive part of the light emitted from the light source and reflect the light to the outer lens; characterised in that the outer lens is configured to reflect part of the light from the flange portion to the upper extension portion; and the upper extension portion is configured to reflect the light from the outer lens outward. a housing having an opening; an outer lens configured to form a lighting chamber together with the housing by being attached to the housing so as to close the opening of the housing; a light source configured to include a light emitting device; a mounting substrate configured to allow the light source to be mounted thereon; a reflector configured to reflect light emitted from the light source; and an extension, wherein: the light source, the mounting substrate, the reflector, and the extension are housed in the lighting chamber; the light source, the reflector, the extension, and the outer lens constitute an optical system; the vehicle lighting fixture further comprises a substrate holder arranged in an upper half portion of the lighting chamber, the mounting substrate being attached to the substrate holder to hold the mounting substrate; the reflector is arranged in a lower half portion of the lighting chamber below the mounting substrate; the extension is arranged in front of the substrate holder and the reflector; the outer lens is positioned in front of the extension; the extension includes a window hole portion positioned in front of the reflector, an upper extension portion configured to extend from an upper edge portion of the window hole portion upward, and an annular flange portion configured to extend from respective outer rim portions of the window hole portion and the upper extension portion rearward; the reflector is configured to receive the light emitted from the light source and reflect the light so that the light can pass through the window hole portion and the outer lens to be projected outward; the flange portion of the extension is configured to receive part of the light emitted from the light source and reflect the light to the outer lens; characterised in that the outer lens is configured to reflect part of the light from the flange portion to the upper extension portion; and the upper extension portion is configured to reflect the light from the outer lens outward. the light source, the mounting substrate, the reflector, and the extension are housed in the lighting chamber; the light source, the reflector, the extension, and the outer lens constitute an optical system; the vehicle lighting fixture further comprises a substrate holder arranged in an upper half portion of the lighting chamber, the mounting substrate being attached to the substrate holder to hold the mounting substrate; the reflector is arranged in a lower half portion of the lighting chamber below the mounting substrate; the extension is arranged in front of the substrate holder and the reflector; the outer lens is positioned in front of the extension; the extension includes a window hole portion positioned in front of the reflector, an upper extension portion configured to extend from an upper edge portion of the window hole portion upward, and an annular flange portion configured to extend from respective outer rim portions of the window hole portion and the upper extension portion rearward; the reflector is configured to receive the light emitted from the light source and reflect the light so that the light can pass through the window hole portion and the outer lens to be projected outward; the flange portion of the extension is configured to receive part of the light emitted from the light source and reflect the light to the outer lens; characterised in that the outer lens is configured to reflect part of the light from the flange portion to the upper extension portion; and the upper extension portion is configured to reflect the light from the outer lens outward.