Webbing winding device and clutch mechanism

A webbing winding device in which a breadth dimension of a torque limiter (90) is less than an axial direction dimension of an external gear (102). A rotation disc (140), the torque limiter (90) or the like is wholly disposed, along a radial direction of the external gear (102), between the external gear (102) and a peripheral wall (96) of a baseplate (92). Further, members such as pawls (130), a rotation disc (140) and the like are disposed, along a radial direction of the peripheral wall (96), between the peripheral wall (96) and an adaptor, and these members are accommodated at an inner side of the external gear (102). Consequently, a thickness dimension (axial direction dimension) of a clutch is practically the same as an axial direction dimension of the external gear (102), and this is extremely thin.