Disclosed is a spin-based semiconductor laser source capable of generating a completely circularly polarized laser light by injecting current into p-type and n-type half-metal magnetic semiconductor layers. Each of the p-type and n-type half-metal magnetic semiconductor layers is prepared by doping a magnetic semiconductor with a transition metal atom and optionally with an acceptor or donor. Alternatively, each of the p-type and n-type half-metal magnetic semiconductor layers is prepared by providing a gate to a magnetic semiconductor and adjusting/controlling its ferromagnetic state according to the field effect. The present invention can solve the problem concerning the insufficient degree of circular polarization in conventional circular-polarization semiconductor laser sources.