A serrated portion is formed on an outer peripheral portion of a lock base body of a lock base of a webbing take-up device. Furthermore, a flange portion is formed on the outer peripheral portion of the lock base body. The flange portion is disposed on a vehicle front side with respect to the serrated portion. Triangular grooves of the serrated portion are closed by the flange portion. When the lock base becomes displaced in a vehicle rearward direction and the flange portion comes into abutting contact with a leg plate of a frame, further displacement of the lock base in the vehicle rearward direction is blocked. Due to this, engagement between the serrated portion and ratchet teeth of a ratchet hole in the leg plate can be maintained.