A vehicular rotatable lamp unit includes a main seat adapted to be mounted on a vehicle, a lamp seat assembly connected pivotally to the main seat, a conducting wire, a first contact assembly mounted on the main seat, and a second contact assembly adapted to be connected to a power source of the vehicle. The conducting wire has a first end connected electrically to the lamp seat assembly, and a second end opposite to the first end. The first contact assembly includes a first contact member connected electrically to the second end of the conducting wire and rotatable along with the lamp seat assembly. The second contact assembly includes a second contact member to contact the first contact member.