The development of semiconductor lasers with on-chip controllability of the beam direction is important for a wide range of applications, including mobile laser projection displays(1), advanced laser printers(2) and chip-to-chip optical communication(3). Here, we report a novel concept to realize such beam-steering lasers using photonic crystals. Our idea is based on the generation of artificial lasing band edges in the photonic band structure, which determine the resonant condition and output beam direction(4-12). We show that the lasing band edge can be tuned by using a composite photonic-crystal structure composed of both square and rectangular lattices, and by varying their relative lattice constants. We demonstrate that lasers based on such composite photonic-crystal structures are able to emit beams in a range of directions that can be dynamically controlled by on-chip integration.