The invention discloses a side reflector pasting device for a light guide plate, and a machining method. The device comprises an induction unit, a clamping unit, a movement unit, a cutting unit, a control unit, and an auxiliary movement unit. The induction unit is used for detecting the position of a machined light guide plate, and the clamping unit is used for clamping the light guide plate for movement. The movement unit is used for the side reflector transmission movement, and the cutting unit is used for cutting a side reflector. The control unit is used for controlling the induction unit, the clamping unit, the movement unit and the cutting unit for the side reflector pasting movement of the light guide plate. The device does not need to carry out the manual reflection of the light guide plate, prevents manual operation from causing burr and pollution at a side edge of the light guide plate through an automatic apparatus, improves the machining precision and quality of the light guide plate, effectively reduces the defective percentage of machined parts, saves the manpower, and reduces the cost.