Child seat

A child seat comprises a main body (2), a seat portion (3) which is supported by the main body so as to be movable in a longitudinal direction, a back portion (4) which is connected to the main body so as to be pivotable around an axis in a lateral direction and be movable within a predetermined range in a direction orthogonal to the axis, and which is pivotally connected to a rear end part of the seat portion on a lower end side thereof, and a restraint belt (22) which is drawn out to a rear side of the back portion from a restraint position on an upper surface side of the seat portion through the back portion, and which is extended to a restraint position on a front end part of the seat portion via a lower surface side of the seat portion. The childe seat is provided with a belt position regulating device (35) for moving the restraint belt which is arranged around the rear end part of the seat portion backward from the back surface (4a) of the back portion.