A de-skewing mechanism for de-skewing a printing medium is disclosed. The printing medium is conveyed by a conveying mechanism in a first linear velocity. The de-skewing mechanism includes a first calibrating roller, a second calibrating roller and a first torque limiting member. The first calibration roller is utilized for conveying a first side of the printing medium in a second linear velocity greater than the first linear velocity, and the second calibrating roller is utilized for conveying a second side of the printing medium in the second linear velocity. The first torque limiting member is coupled to the first calibrating roller and is utilized for stopping driving the first calibrating roller when the first side of the printing medium reaches a predetermined tension, such that the second side of the printing medium is capable of proceeding relative to the first side, so as to be aligned with the first side.