The bottleneck of a three-dimensional structural analysis of protein molecules is the crystallization of large (>0.1μm) and suitable high quality crystals. To overcome this difficulty, magnetic field effects have been studied intensively in recent years. Here, we outline the magnetic field effects on the crystallization of protein. Crystallization of hen eggwhite lysozyme was carried out under a static and homogeneous magnetic field of 0-11 T. It is clearly demonstrated that a magnetic field decreased the number of nuclei that appeared and not only oriented the crystals but also changed the crystal habit. The magnetic field effects on the orientation and growth rate of the crystals were further investigated. The degree of orientation of the crystals depends on crystal growth rate and container geometry, in addition to magnetic field strength. The magnetic field decreases the growth rate of the crystals and also the flow rate of the buoyancy convection in an electrolyte solution.