An LED tube lamp comprises a lamp tube, two light boards disposed in the lamp tube having a plurality of light sources mounted thereon, two lamp caps respectively disposed at both ends of the lamp tube and having a power supply disposed in the lamp caps, and a support unit. The power supply comprises a circuit board. The support unit is configured to fix the light board and comprises a main body and a support arm. The support arm is disposed on the main body and abutted to the inner surface of the lamp tube, so that the support unit can support the inner surface of the lamp tube.