A sub tank (40) which is mounted in an inkjet printer including an inkjet head for discharging UV ink and supplies UV ink to the inkjet head includes a space forming unit (41) which forms a space (40a) including an ink storage chamber (40b) for storing UV ink and a pump communication port communicating with a pump for making a pressure in the space (40a) negative, and a liquid-proof ventilation filter (44) which is disposed in the space (40a), allows gas to be circulated, and does not allow the UV ink to be circulated so as to prevent the UV ink from flowing out from the space (40a) to the pump communication port.