A coupling structure which couples an ink container to a supply target includes a cap and a joint. The cap includes a container side communication path and a container opening/closing valve. The container side communication path is communicated with a supply port. The container opening/closing valve opens and closes the supply port. The joint includes a main body side communication path, a main body opening/closing valve and a first biasing member. The main body side communication path is communicated to an inflow port. The main body opening/closing valve opens and closes the inflow port. The first biasing member biases the main body opening/closing valve to a side of the ink container. The main body opening/closing valve is protruded to a side of the ink container closer than the inflow port even if the first biasing member is mostly contracted.