A clamping apparatus includes a receiving frame, a guide plate, two drive assemblies, and two clamping assemblies. The receiving frame includes two parallel securing arms and a connection arm. The securing arms and the connection arm define a first receiving space. Each of the securing arms defines a slot. The guide plate is configured for mounting of a workpiece thereon. The drive assemblies are configured for cooperatively moving the guide plate between a first position and a second position. When the guide plate is located at the first position, the workpiece is loaded on the guide plate and distant from the connection arm. When the guide plate is located at the second position, the workpiece is adjacent to the connection arm and entirely received in the first receiving space and the slots. The clamping assemblies are configured for cooperatively clamping the workpiece.