A mechanism for positioning a stylus inside an electronic device is provided. The stylus positioning mechanism comprises a position-limiting element, a pen cap, a pushing element, a linking rod, a stopping block and a repositioning element. The position-limiting element has an accommodating space for housing the stylus. The pen cap is disposed at one end of the position-limiting element for gripping the stylus. The pushing element is fastened to the pen cap for pushing the stylus out from the position-limiting element. The linking rod is fastened to the pen cap so that it moves together with the pen cap. The stopping block is disposed on the side edge of the position-limiting element for restricting the movement of the linking rod in the latched position or the unlatched position. The repositioning element is fastened to the stopping block for repositioning the stopping block to the latched position.