Detecting method about external cable and output control method of portable device

A method for detecting the connection of a cable and a method for controlling the output of a portable terminal are provided to shut off the output of an embedded display and allow only an external output automatically so that power consumption is reduced. The connection of a cable and a portable terminal is detected(S100). An external output signal becomes in an off state and the power of a display embedded in the portable terminal is turned on if the cable is not connected(S120,S130). The display is turned off, and a signal is transmitted to the cable if the cable is connected. The power state of the portable terminal is checked frequently or periodically(S160). The connection of the cable is detected by using a hot plug detect(HPD), embedding a switch in a jack, or using a ground path.