An optical sensor including a substrate and a plurality of pixel units are provided. The pixel units are disposed on the substrate, and each of the pixel units includes a light source element, a light sensor element, a circuit unit, and an isolation element. Herein, the light source element emits light, the light sensor element senses an optical image. The circuit unit is configured to drive the light source element to emit light and to drive the light sensor element to sense the optical image. The isolation element isolates the light sensor element from the light source element. In addition, the light source element is disposed between the isolation element of the respective pixel unit and an isolation element of a neighboring pixel unit.