Transient three-dimensional numerical computations were carried out for the convection of silicon melt in a Czochralski configuration under a cusp-shaped magnetic field. Numerical conditions are Ha = 0 and 161 with Pr = 0.013, Ra = 3.92 × 10 5, Recr 1329, and Recu = -1596. Computed results show elliptic velocity and temperature profiles near the top of the melt that rotate in a circumferential direction of a crucible even under an axially symmetric cusp-shaped magnetic field at Ha = 161. Elliptic velocity and temperature distributions were stable but oscillating as a function of time. Velocity and temperature oscillation became a rather regular periodic structure under a cusp-shaped magnetic field in comparison with the nonmagnetic case.