A seat belt device for adjusting the tension of a seat belt webbing drawn across a user's body when the seat belt is in a latched condition, the seat belt device comprising: a housing defining a receiving area configured to slidably receive the seat belt webbing therethrough; a clamp member slidably mounted to the housing, the clamp member being configured for movement between a first position and a second position, wherein a clamping surface of the clamp member urges a portion of the seat belt webbing against an engagement portion of the housing when the clamp member is in the first position, the engagement portion being included in the receiving area; and a biasing member being configured to urge the clamp surface toward the engagement portion.