Apparatus and method for controlling width of direct endless hot rolling line between continuous casting and hot rolling

The invention provides an apparatus and a method for controlling a width in a direct endless hot rolling line between continuous casting and hot rolling. The apparatus for controlling a width according to one embodiment of the present invention is an apparatus for controlling a width in a direct endless hot rolling line between continuous casing and hot rolling of a mini mill including a continuous casting machine, a roughing mill, a heating device, and a finishing mill, comprising: a tension control unit for controlling the tension between the roughing mill and the finishing mill so as to obtain a target tension value; a width measurement unit for measuring an output side width of the finishing mill; and a width control unit for controlling the tension control unit so as to change the target tension value when the measured output side width of the finishing mill is different from a target width.