Effect of horizontal strong static magnetic field on swimming behavior of Paramecium caudatum was studied by using a superconducting magnet. Around a center of a round vessel, random swimming at 0 T and aligned swimming parallel to the magnetic field (MF) of 8 T were observed. Near a wall of the vessel, however, swimming round and round along the wall at 0 T and aligned swimming of turning at right angles upon collision with the wall, which was remarkable around 1~4 T, were detected. It was experimentally revealed that the former MF-induced parallel swimming at the vessel center was caused physicochemically by the parallel magnetic orientation of the cell itself. From magnetic field dependence of the extent of the orientation, the magnetic susceptibility anisotropy (χ‖-χ⊥) was first obtained to be 3.4×10-23 emu cell-1 at 298 K for Paramecium caudatum. The orientation of the cell was considered to result from the magnetic orientation of the cell membrane. On the other hand, although mechanisms of the latter swimming near the vessel wall regardless of the absence and presence of the magnetic field are unclear at present, these experimental results indicate that whether the cell exists near the wall alters magnetic field effect on the swimming in the horizontal magnetic field.