Method of designing reflective surface of reflector in vehicle lamp

A method of designing a reflective surface of a reflector used in a vehicle lamp, comprising:

• a first base curve generating step of generating a first base curve on a first base plane including an optical axis passing a light source position where a light source is placed and becoming a direction into which light from said light source is reflected by the reflector, and a first base axis perpendicular to said optical axis;
• a second base curve generating step of generating a plurality of second base curves extending in a direction of a second base axis perpendicular to said first base plane, for said first base curve;
• and
• a surface shape generating step of generating a surface shape of said reflective surface, based on said first base curve and said plurality of second base curves,
• wherein said first base curve generating step comprises repeating a step of generating one partial curve and thereafter generating a subsequent partial curve so as to be connected to said partial curve, thereby generating one said first base curve consisting of a plurality of said partial curves connected to each other, and
• wherein each said partial curve is generated based on a shape parameter according thereto.