An ink feeding mechanism includes an ink reservoir 31, a subtank 32 for temporarily storing ink, a decompression channel 44 for decompressing the subtank 32 to a fixed pressure, an ink force-feed channel 41 interconnecting the ink reservoir 31 and subtank 32, a first switch valve 35 mounted on the ink force-feed channel 41, a communication channel 43 interconnecting the subtank 32 and an inkjet head 10, an ink circulating channel 42 interconnecting the communication channel 43 and ink reservoir 31, and a second switch valve 34 mounted on the ink circulating channel 42. A lid member 51 forming part of a chamber has a pressure regulating channel 45 connected thereto, which is connected also to a force-feed channel 46 with a pressure pump 37 mounted thereon, and an exhaust channel 47 with an exhaust pump 38 mounted thereon.