A handwriting input apparatus comprises a position-encoding layer and a pen. The position-encoding layer comprises a plurality of position-encoding pattern. The position-encoding layer is transparent to visible light and is reflective to light of predetermined wavelengths. Each position-encoding pattern represents a specific code. The pen has a projector and a camera at one end. The projector is adapted to generate a light beam of the predetermined wavelengths toward the position-encoding layer. The camera is adapted to capture images of the plurality of position-encoding pattern.