A lamp includes a lamp tube, a carrier, a light bar circuit board, a driver circuit board, a plurality of first luminous elements and a parallel-connected type luminous unit. The carrier is accommodated in the lamp tube. The light bar circuit board is disposed on the carrier. The driver circuit board is disposed on the carrier and adjoins the light bar circuit board. The first luminous elements are disposed on the light bar circuit board. The parallel-connected type luminous unit is disposed on the driver circuit board, and includes a plurality of luminous element groups connected in parallel.