An optical detection apparatus includes a substrate, a light source, a light sensor, a light-guiding structure. The substrate has a top surface. The light source on the top surface is configured to generate detection light toward an object over the light source. The light sensor is located on the top surface. The light-guiding structure is above the top surface and at least partially above the light source. A central axis of the light-guiding structure is vertical to the top surface, and the light source and the light sensor are at opposite sides relative to the central axis. The light-guiding structure is configured to deflect the detection light from one of the opposite sides at which the light source is located to another one of the opposite side at which the light sensor is located, such that the detection light reflected by the object moves toward the light sensor.