In a webbing take-up device, an open portion is formed in the other side, in a direction about a rotational axis of a switch pawl, of a sensor holder. In a state where an engagement piece is positioned on the outside of the open portion, the switch pawl is rotated about a shaft to cause the engagement piece to enter in a window portion, so, a distal end of the engagement piece, bent in a hook shape, faces to a regulation wall in an axial direction of the shaft. It is not necessary to elastically deform the engagement piece when bringing the regulation wall and the engagement piece into facing. Therefore, the engagement allowance in the engagement piece with the regulation wall can be enlarged and the distal end of the engagement piece can be prevented from crossing over the regulation wall and moving toward the shaft side.