An additive container is configured to contain an additive to be added to a defibrated material therein and to be coupled to an intake port for introducing the additive of an additive supply device. The additive container includes a container that includes a discharge port and contains the additive, and a first shutter member that opens and closes the discharge port. The first shutter member enters an open state by rotating the container in a first direction around a central axis of the discharge port with respect to the first shutter member, and the first shutter member enters a closed state by rotating the container in a second direction opposite to the first direction with respect to the first shutter member from the open state.