An optical touch apparatus is adapted to a display apparatus. The optical touch apparatus includes at least one light source, at least one light guide unit, and at least one optical detector. The light source is disposed beside a display area of the display apparatus and capable of providing a light beam. The light guide unit is disposed beside the display area in a transmission path of the light beam and has a first surface, a second surface opposite to the first surface, and a light incident surface. The light incident surface connects the first and second surfaces. The light beam is capable of entering the light guide unit through the light incident surface and is transmitted to a sensing space in front of the display area. The optical detector is disposed beside the display area to sense an intensity variation of the light beam in the sensing space.