A seat belt retractor including at least a spool that retracts a seat belt that restricts an occupant, the seat belt retractor comprising: a vehicle sensor that operates in an emergency in which a deceleration that is larger than a deceleration applied to a vehicle at normal times is applied, the vehicle sensor having a function of stopping rotation of the spool in a seat belt withdrawal direction; a webbing sensor that operates when the seat belt is rapidly withdrawn at a rate that is larger than a withdrawal rate at normal times, the webbing sensor having a function of stopping the rotation of the spool in the seat belt withdrawal direction; a vehicle sensor function/webbing sensor function cancellation control mechanism that controls cancellation of the function of the vehicle sensor and cancellation of the function of the webbing sensor; and a cancellation-cancelling prevention unit that, when a large load with respect to a load applied at normal times is applied to the vehicle sensor function/webbing sensor function cancellation control mechanism from the vehicle sensor while in a state in which the vehicle sensor function/webbing sensor function cancellation control mechanism has canceled the function of the vehicle sensor, prevents the cancellation of the function of the vehicle sensor from being canceled due to the large load performed by the vehicle sensor function/webbing sensor function cancellation control mechanism, characterized in that the vehicle sensor function/webbing sensor function cancellation control mechanism includes, a control lever (22, 23) that is operated and controlled between a cancellation position that cancels the vehicle sensor function/webbing sensor function and a cancellation cancelling position that cancels the cancellation of the vehicle sensor function/webbing sensor function, a control cam member that abuts the control lever to the cancellation position by rotating together with the rotation of the spool and that maintains the control lever at the cancellation position, and a lever biasing spring (24, 25) that constantly biases the control lever in the direction of the cancellation cancelling position, wherein the control lever which is the control lever that is maintained at the cancellation position, being abutted by the control cam member when the control lever is in the cancellation position. a vehicle sensor that operates in an emergency in which a deceleration that is larger than a deceleration applied to a vehicle at normal times is applied, the vehicle sensor having a function of stopping rotation of the spool in a seat belt withdrawal direction; a webbing sensor that operates when the seat belt is rapidly withdrawn at a rate that is larger than a withdrawal rate at normal times, the webbing sensor having a function of stopping the rotation of the spool in the seat belt withdrawal direction; a vehicle sensor function/webbing sensor function cancellation control mechanism that controls cancellation of the function of the vehicle sensor and cancellation of the function of the webbing sensor; and a cancellation-cancelling prevention unit that, when a large load with respect to a load applied at normal times is applied to the vehicle sensor function/webbing sensor function cancellation control mechanism from the vehicle sensor while in a state in which the vehicle sensor function/webbing sensor function cancellation control mechanism has canceled the function of the vehicle sensor, prevents the cancellation of the function of the vehicle sensor from being canceled due to the large load performed by the vehicle sensor function/webbing sensor function cancellation control mechanism, characterized in that the vehicle sensor function/webbing sensor function cancellation control mechanism includes, a control lever (22, 23) that is operated and controlled between a cancellation position that cancels the vehicle sensor function/webbing sensor function and a cancellation cancelling position that cancels the cancellation of the vehicle sensor function/webbing sensor function, a control cam member that abuts the control lever to the cancellation position by rotating together with the rotation of the spool and that maintains the control lever at the cancellation position, and a lever biasing spring (24, 25) that constantly biases the control lever in the direction of the cancellation cancelling position, wherein the control lever which is the control lever that is maintained at the cancellation position, being abutted by the control cam member when the control lever is in the cancellation position.