The remanent magnetization of meteorite material in the solar system indicates that magnetic fields of some Gauss were present in the early protoplanetary disk. It is shown that such relatively strong magnetic fields can be generated in dusty protoplanetary disks by relative shear motions of the charged dust and the neutral gas components. The ultimate energy source is the gravitational field of the stellar object that results in a sheared accretion flow. Self-consistent multi-fluid simulations show that for plasma parameters typical for protoplanetary disks shear flows with collisional momentum transfer between the different components of the dusty plasma result in a very efficient generation of magnetic fields with strengths of about 0.1-1 Gauss on spatial scales of two astronomical units in about two years. Such strong magnetic fields should influence the coupling of the stellar dipole field and the disk, the accretion flow, stellar winds and jets and the formation of protoplanetary objects.