A lamp tube includes a lamp shade, connectors fixed to opposite ends of the lamp shade, and a circuit board received in the lamp shade and electrically connected with the connectors. At least two resilient members protrude from opposite sides of the circuit board. Each resilient member is resiliently deformed and urged into contact with an inner surface of the lamp shade. The deformation of the at least two resilient members is for providing a spring push force to the circuit board, thus causing the circuit board to tightly engage the inner surface of the lamp shade, thereby retaining the circuit board in position inside the lamp shade.