A detection device for detecting an insertion depth of a terminal of a cable connector inside a housing of the cable connector includes a positioning assembly and a detection assembly. The positioning assembly positions the housing of the cable connector. The detection assembly includes a first driving device, a sensing element mounted on the first driving device and movable by the first driving device, and a displacement sensor mounted on the first driving device and movable in a moving direction of the sensing element by the first driving device. The displacement sensor is connected to the sensing element and senses a displacement of the sensing element.