A rotatable tray is installed on a child seat for accommodating a container, and the rotatable tray includes a platform, a fixing base, a positioning base, a resilient component and a supporting base. The platform includes a communicating chamber, and the fixing base is fixed in the communicating chamber. The positioning base includes a first engaging portion, and the positioning base is slidably disposed in the communicating chamber. The resilient component is disposed between the fixing base and the positioning base. The supporting base is connected to the platform, an engaging base protrudes from an end of the supporting base, and a second engaging portion is disposed on the supporting base. The engaging base is pivoted in the communicating chamber so that the platform can rotate relative to the supporting base. The resilient component drives the first engaging portion to selectively engage with the second engaging portion.