A structure which ensures a movement of a seal lip disposed in a seal lip is realized by preventing foreign matters from permeating a seal internal space between a slinger and a seal ring. A labyrinth seal is disposed between an outer peripheral edge of a rotary side annular portion configuring the slinger and an inner peripheral surface of a stationary side cylindrical portion of a metal insert configuring the seal ring. In addition, a thickened portion is formed in a portion of an elastic member configuring the seal ring over an entire periphery. An auxiliary seal lip whose rigidity is lower than that of respective seal lips is disposed in the thickened portion over the entire periphery. The auxiliary seal lip prevents the foreign matters from adhering to the seal lip, and prevents the movement of the seal lip from being hindered.