A pair of terminal portions of a bus bar is composed of a first terminal portion and a second terminal portion extended along a sidewall of the base portion. Each of the first and second terminal portions has a spring portion for generating biasing force toward a direction of holding the base portion, and a contact portion provided on a tip of the spring portion. The contact portion of the first terminal portion abuts on a contact lead wire, and the contact portion of the second terminal portion abuts on the sidewall of the base portion, thereby the contact portions hold the base portion therebetween. In a natural condition that the bulb is not inserted and the spring portion is not elastically deformed, the pair of terminal portions is displaced from a center plane toward the one side corresponding to a projection size of the contact lead wire.