A continuous variable valve duration system includes a camshaft, a first cam portion including a first cam, into which the camshaft is inserted and of which a relative phase angle of the first cam with respect to the camshaft is variable, an inner bracket for transmitting rotation of the camshaft to the first cam portion, a slider housing into which the inner bracket is rotatably inserted, on which a control slot is formed, and the slider housing being rotatable around a pivot shaft, a first rocker arm of which a first end contacts with the first cam and of which a second end is connected to a first valve, a rocker shaft of which the first rocker arm is rotatably connected thereto and of which an eccentric shaft inserted into the control slot is formed thereto, and a control portion for rotating the rocker shaft for the slider housing to be moved with respect to the camshaft.