A deep groove ball bearing includes an outer ring, an inner ring, a retainer and steel balls, where the retainer is disposed between the outer ring and the inner ring, sockets are disposed on the retainer, the steel balls are disposed in the sockets, the retainer is formed by two retainer bodies which are separated from each other, grooves are formed in the retainer bodies at intervals, the grooves in one retainer body are combined with the grooves in the other retainer body to form the sockets, each retainer body is provided with a plurality of sub-connectors which are separated from each other, a first connecting block and a second connecting block are formed at two ends of each sub-connector respectively, two grooves are formed in each sub-connector, and a positioning table is disposed between the two grooves in each sub-connector.