Novel crystals of a potassium salt of (E)-N-[6-methoxy-5-(2-methoxyphenoxy)-2-(pyrimidin-2-yl)pyrimidin-4-yl]-2-phenylethenesulfonamide, a preparation process thereof, and novel solvates of (E)-N-[6-methoxy-5-(2-ethoxyphenoxy)-2-(pyrimidin-2-yl)pyrimidin-4-yl]-2-phenylethenesulfonamide.