A connection device of a portable terminal is provided. The connection device includes one or more coupling slots provided on a lateral side of the portable terminal, one or more metal pads mounted on a bottom of the one or more coupling slots, and a plug including one or more magnets corresponding to the one or more pads. The one or more magnets are arranged to protrude toward a predetermined side of the plug, and inserted into the one or more coupling slots by an attractive force produced between the one or more metal pads and the one or more magnets, thereby coupling the plug to the lateral side of the portable terminal.