The invention relates to an apparatus and method for measuring the position of a gas bubble in a bubble level and a bubble level comprising the apparatus. The bubble level comprises a cylindrical sealed housing. The sealed housing is partially filled with liquid and contains the gas bubble. The apparatus comprises: at least two light-emitting devices, the light emitted from each light-emitting device illuminating the gas bubble and an inner bottom surface of the bubble level; and at least two receiving devices, each receiving device receiving the light that is reflected by the inner bottom surface of the bubble level and reflected and refracted by the gas bubble and converting it into electrical signals, the electrical signals being processed for calculating the position of the gas bubble, wherein each of the at least two light-emitting devices and each of the at least two receiving devices being alternatively disposed at the periphery of the cylindrical sealed housing.