A smart door apparatus includes an actuator and a harness (100). The actuator is installed at a door (D) rotatably connected with a cabin (C) of the construction machine via a hinge mechanism (UH, LH). The actuator may be configured to operate a locking apparatus of the door by signals of a smart key (99). The harness (100) is arranged in an axial direction (X) of the hinge mechanism (UH, LH) to supply electricity to the actuator. Thus, only torsion may be applied to the harness regardless of rotation angles of the door to increase a lifespan of the harness (100).