A sealing device for a wheel bearing, comprising: a first insert body comprising an annular first frame and a first sealing part coupled to the first frame; and a second insert body comprising an annular second frame having a diameter that is smaller than that of the first frame and a second sealing part coupled to the second frame, wherein: the second insert body is configured to be rotated relative to the first insert body about a rotation axis, the first insert body and the second insert body are arranged such that a gap is formed between the first sealing part and the second sealing part, characterized that the first sealing part and the second sealing part are formed to define a first cavity having an annular shape based on the rotation axis, a first cavity passage connected to the first cavity and having an annular shape based on the rotation axis, and a second cavity connected to the first cavity passage and having an annular shape based on the rotation axis in the gap, the first sealing part comprises a first lip protruding toward the second sealing part, having an annular shape based on the rotation axis and configured to partially define the first cavity, the second sealing part comprises a second lip protruding toward the first sealing part, having an annular shape based on the rotation axis and configured to partially define the second cavity, the first lip comprises at least one groove on a radially outer surface thereof facing the first cavity, the second lip comprises at least one groove on a radially outer surface thereof facing the second cavity, the second sealing part comprises a first baffle having an annular shape based on the rotation axis, the first lip comprises a second baffle spaced apart from the first baffle in the radially inward direction and having an annular shape based on the rotation axis; and the first baffle and the second baffle partially define the first cavity passage, a width of the groove exceeds 0.1 mm. a first insert body comprising an annular first frame and a first sealing part coupled to the first frame; and a second insert body comprising an annular second frame having a diameter that is smaller than that of the first frame and a second sealing part coupled to the second frame, wherein: the second insert body is configured to be rotated relative to the first insert body about a rotation axis, the first insert body and the second insert body are arranged such that a gap is formed between the first sealing part and the second sealing part, characterized that the first sealing part and the second sealing part are formed to define a first cavity having an annular shape based on the rotation axis, a first cavity passage connected to the first cavity and having an annular shape based on the rotation axis, and a second cavity connected to the first cavity passage and having an annular shape based on the rotation axis in the gap, the first sealing part comprises a first lip protruding toward the second sealing part, having an annular shape based on the rotation axis and configured to partially define the first cavity, the second sealing part comprises a second lip protruding toward the first sealing part, having an annular shape based on the rotation axis and configured to partially define the second cavity, the first lip comprises at least one groove on a radially outer surface thereof facing the first cavity, the second lip comprises at least one groove on a radially outer surface thereof facing the second cavity, the second sealing part comprises a first baffle having an annular shape based on the rotation axis, the first lip comprises a second baffle spaced apart from the first baffle in the radially inward direction and having an annular shape based on the rotation axis; and the first baffle and the second baffle partially define the first cavity passage, a width of the groove exceeds 0.1 mm. the second insert body is configured to be rotated relative to the first insert body about a rotation axis, the first insert body and the second insert body are arranged such that a gap is formed between the first sealing part and the second sealing part, characterized that the first sealing part and the second sealing part are formed to define a first cavity having an annular shape based on the rotation axis, a first cavity passage connected to the first cavity and having an annular shape based on the rotation axis, and a second cavity connected to the first cavity passage and having an annular shape based on the rotation axis in the gap, the first sealing part comprises a first lip protruding toward the second sealing part, having an annular shape based on the rotation axis and configured to partially define the first cavity, the second sealing part comprises a second lip protruding toward the first sealing part, having an annular shape based on the rotation axis and configured to partially define the second cavity, the first lip comprises at least one groove on a radially outer surface thereof facing the first cavity, the second lip comprises at least one groove on a radially outer surface thereof facing the second cavity, the second sealing part comprises a first baffle having an annular shape based on the rotation axis, the first lip comprises a second baffle spaced apart from the first baffle in the radially inward direction and having an annular shape based on the rotation axis; and the first baffle and the second baffle partially define the first cavity passage, a width of the groove exceeds 0.1 mm.