This utility model is provide a locking device of car covers for pick-up trucks composing a swing stem and a lock hook inserted and deposited on the swing stem, the end part of the swing stem is inserted into a locking swing handle, a hinge block is disposed on the car cover, which is characterized in that the top of the swing stem is positioned and hinged on the hinge block. The advantages of this utility model are summarized as: to overcome the sliding friction of existing lock devices, to enhance the force born by the main body of device and to increase the flexibility of the swing stem.