A car safety seat is disclosed in the invention, including a main body and a flexible layer. Multiple air vents are formed on the main body and penetrate through the main body along a front-to-rear direction. The flexible layer is formed on a surface of the main body and in the air vents. The multiple air vents enable vapor to pass through the main body without being blocked by the main body during a foaming process, which thereby allows foaming particles to fully contact with the vapor to ensure an enhanced foaming effect. Also, the flexible layer is not only formed on the surface of the main body but also formed in the air vents to fill the air vents, and thereby the flexible layer is more tightly combined with the main body to reduce a risk of detachment from the main body.