A power trunk device includes a hinge arm coupled to a trunk lid and configured to be rotatably coupled to a vehicle body panel to define a trunk space, the hinge arm being configured to open and close the trunk lid, a torsion bar link rotatably coupled to a middle of the hinge arm, a torsion bar connected between the torsion bar link and the vehicle body panel in front of the hinge arm, the torsion bar being configured to provide elastic force in a direction in which the trunk lid is opened, and an electric drive unit connected between the hinge arm and the torsion bar, the electric drive unit being configured to be moved together with the hinge arm while providing rotational force to the hinge arm.