A child seat includes a seat body having a seat portion, a backrest, and right and left side guards; and a cushion disposed on an outer side surface of the side guards. The cushion may include a gasbag filled with gas. The child seat may further include vent portion for discharging the gas in the gasbag when a gas pressure in the gasbag exceeds a predetermined pressure. When a high load is exerted on the gasbag, the gas is discharged through the vent portion, thereby absorbing a shock.