The invention relates to a flexible printing circuit holding mechanism of an actuator assembly of a hard disk drive including a flexible printing circuit holder protruding from an arm-mold of the actuator assembly, and an flexible printing circuit clip that is mounted to the flexible printing circuit holder so as to be rotatable relative to the flexible printing circuit holder. The flexible printing circuit holder defines a guide groove into which the flexible printing circuit is inserted and a first side support plate facing one side surface of the flexible printing circuit. The flexible printing circuit clip includes a second side support plate juxtaposed with the first side support plate and facing the other side surface of the flexible printing circuit, and at least two clip arms extending in a horizontal direction over upper and lower edges of the flexible printing circuit, respectively. At least one of the clip arms has a hook that is hooked onto the first side support plate. The flexible printing circuit holding mechanism thus prevents a portion of the flexible printing circuit from moving in vertical and horizontal directions.