Under a strong magnetic field, the diamagnetic properties of biological cells modulate the behavior of the cells themselves, under conditions of both floating and adherence. The morphological effects of strong static magnetic fields on adherent cells are less well understood than the effects of magnetic fields on red blood cells. In the present study, a high-intensity magnetic field of 14 T affected the morphology of smooth muscle cell assemblies, and the shapes of the cell colonies extended along the direction of the magnetic flux. The phenomenon was most notable under magnetic fields of more than 10 T, where an ellipsoidal pattern of smooth muscle cell colonies was clearly observed. The ellipticity of the cell colony pattern with a 14-T magnetic field was 1.3, whereas that with a field of 0–8 T was close to a circle at about 1.0. The evidence that smooth muscle cells detect high-density magnetic flux and thus change their cell orientation was shown as a visible pattern of cellular colonies. The speculated mechanism is a diamagnetic torque force acting on cytoskeleton fibers, which are dynamically polymerizing–depolymerizing during cell division and cell migration.