A vehicular headlamp has a reflector which is so optically designed as to provide, by reflecting light from a light source, a basic beam pattern of approximately semicircular shape wholly disposed below the horizon, with a top edge cutoff extending horizontally. A front lens is stepped to produce a lower beam pattern by raising part of the basic beam pattern and by horizontally expanding the rest of the basic beam pattern. The top edge cutoff of the lower beam pattern is as clearcut as that of the basic beam pattern. Either of two different lower beam patterns required for vehicles keeping to the right and for those keeping to the left is producible merely by changing the optical design of the front lens.
A reflecting mirror, for a vehicle headlamp, which provides a sufficient amount of light near a slant cutoff line in downward-beam light distribution, thereby improving visibility in a long-distance region and a medium-distance region. The reflecting mirror has at least a first reflecting area and a second reflecting area. For a first reflecting area (10B--close to a horizontal reference face (x-y plane) when a reflecting face (10) is viewed from an optical axis direction--a reference curve is set in a slant reference face inclined to the horizontal reference face at an angle equal to an angle (.theta.col) of a slant cutoff line with a horizontal line. For a second reflecting area (10D, 10E)--positioned above or below the first reflecting area (10B) with respect to the horizontal reference face--a reference curve is set in a slant reference face inclined to the horizontal reference face at a second angle larger than 0.degree. and smaller than the angle of the slant cutoff line with the horizontal line. Parabolas are then associated with planes orthogonal to the slant reference face, thereby forming a curved surface.
