Abstract: Systems and techniques are described to provide a bulb insertion structure of a vehicular lamp which allows bulb replacement and accurate positioning of a bulb with respect to a reflector. In general, in one implementation, a bulb insertion structure of a vehicular lamp includes a plurality of fixing protrusions formed on an outer periphery of a rear end portion of a cylindrical socket fixture fixed in a bulb insertion hole of a reflector; a plurality of engaging protrusions formed on an outer periphery of a focus ring provided on a bulb and corresponding to the fixing protrusions; and a cup-shaped socket covering the outer periphery of the socket fixture from the rear, the socket incorporating a spring for pressing forward the rear end portion of the accommodated bulb, and having an outer peripheral wall provided with, at multiple locations corresponding to the fixing protrusions, an engaging notch (J-slot) for holding the engaging protrusion and the fixing protrusion overlapped together.