A reclining device for a vehicle seat includes a housing having one side opened to communicate with an interior of the housing, a clutch drum inserted into the housing, configured to be rotatable, and having one side directed toward the housing and opened to communicate with an interior of the clutch drum, a cam inserted into the clutch drum and configured to receive a rotational force from the outside of the housing and transmit the rotational force to the clutch drum, and a brake drum configured to receive the rotational force from the clutch drum and having a center to which a shaft is coupled, in which a plurality of coupling protrusions is provided on one surface of the cam directed toward the housing, and the coupling protrusions penetrate the other side of the housing and are inserted into coupling holes of a lever bracket.