[en] We point out the possibility that the magnitude of the bare gauge coupling constant is determined theoretically in a composite model of all particles in SUSY theories. We show explicitly in two space-time dimensions that the N L/L SUSY relation (i.e. a SUSY compositeness condition for all particles) between N = 2 L SUSY QED and N = 2 N L SUSY determines the magnitude of the bare electromagnetic coupling constant (i.e. the fine structure constant) of N = 2 L SUSY QED.