A device for transporting magnetic or magnetisable microbeads ( 25 ) in a capillary chamber ( 14 ) comprises a permanent magnet ( 10 ) or an electromagnet ( 11 ) for subjecting the capillary chamber to a substantially uniform magnetic field, to apply a permanent magnetic moment to the microbeads ( 25 ). At least one planar coil ( 22 ) and preferably an array of overlapping coils are located adjacent to the capillary chamber ( 14 ) for applying a complementary magnetic field on the microbeads parallel or antiparallel to said substantially uniform magnetic field, to drive the microbeads. An arrangement is provided for switching the current applied to the coil(s) ( 22 ) to invert the field produced thereby, to selectively apply an attractive or repulsive driving force on the microbeads ( 25 ). The device is usable to transport microbeads for performing chemical and biochemical reactions or assay, as is done for instance in clinical chemistry assays for medical diagnostic purposes.