Disclosed is an optical sensor including a substrate, a redistribution chip structure disposed on the substrate, a sensor chip disposed on the redistribution chip structure, a light-permeable sheet arranged above the sensor chip, metal wires electrically connecting the substrate and the sensor chip, and a package body disposed on the substrate. The redistribution chip structure includes an insulating body, a first electronic chip embedded in the insulating body, and a redistribution layer (RDL) connected to bottoms of the insulating body and the first electronic chip. The RDL is fixed onto the substrate in a flip-chip manner. A projected region defined by orthogonally projecting a sensing area of the sensor chip onto the redistribution chip structure is located inside outer edges of the redistribution chip structure. The redistribution chip structure, the sensor chip, a part of the light-permeable sheet, and the metal wires are embedded in the package body.