A child safety seat includes an inner member, an outer member, and a support frame. The inner member has a seat part and a backrest part that extends upwardly from a rear end and lateral ends of the seat part. The outer member has a rear portion that is disposed behind the backrest part of the inner member, and a front portion that extends from a periphery of the rear portion and that is coupled to the inner member. The support frame includes a first subframe unit that is disposed behind and adjacent to the inner member and that is connected to the outer member, and a second subframe unit that extends between the inner and outer members from the first subframe unit.