A continuous variable valve duration apparatus may include: a camshaft; first and second cam portions on which a cam is formed respectively; first and second inner brackets transmitting rotation of the camshaft to the first and second cam portions respectively; a slider housing in which the first and the second inner brackets are rotatably inserted; first and second guiding portions formed on the slider housing; a control shaft parallel to the camshaft; a control rod eccentrically formed on the control shaft; a positioning protrusion connected to the control shaft; a guide head on which a head guiding portion and a head hole are formed; a cam cap supporting rotations of the first and the second cam portions and guiding movement of the slider housing, a control portion selectively rotating the control shaft; and a stopper unit limiting movement of the positioning protrusion.