Provided is an artificial retina system for improving contrast sensitivity. The artificial retina system includes an artificial retina which is installed under the retina and includes a plurality of photodiode cells and a microcomputer. The microcomputer compares, with at least one reference value, the magnitude of an electric signal outputted from a photodiode in each of the photodiode cells. The microcomputer controls to amplify or reduce the electric signal outputted by each of the photodiode cells according to the result of comparison. Visual cells corresponding to each of the photodiode cells can be stimulated with an electric signal controlled by the microcomputer.