A securing device for bone fastener is provided, which allows the bone fastener to be more securely fixed in position in the fractured bone. The securing device includes a bolt having an elongated portion and a head portion, with the head portion being formed with a threaded through hole which is inclined with respect to the longitudinal axis of the bolt. Moreover, the securing device includes a set screw having a threaded portion which can screw into the threaded through hole in the bolt and which is greater in length than the threaded through hole. In use, the elongated portion of the bolt is inserted through the implantation hole and the opening in the fractured bone; then a hole is drilled through the inclined through hole in the head portion of the bolt; and finally the set screw is screwed through the inclined hole in the head portion of the bolt into the hole in the fractured bone. This allows the securing device to be fixed in position in the fractured bone, thus securing the bone fastener fixedly in position.