A tube bending apparatus for bending a straight lamp tube includes a horizontal heating chamber, a vertical heating chamber and a tube bending mold. The horizontal heating chamber includes a bending tube heating zone and two pre-heating zones. The bending tube heating zone has a working temperature higher than that of the two pre-heating zones. The vertical heating chamber communicates with the horizontal heating chamber and includes a mold heating zone. The mold heating zone has a working temperature higher than or equal to that of the bending tube heating zone. The tube bending mold is heated in the mold heating zone in a working temperature to bend the straight lamp tube held and heated in the horizontal heating chamber.