An ink supply device is provided for supplying ink (10c) to a recording head for discharging the ink in an inkjet printer, that includes: a replaceable ink container (30) being a container for storing the ink (10c) and being replaceable; and a male connector (41) to be inserted into the replaceable ink container (30) to take out the ink (10c) from the replaceable ink container (30), wherein the replaceable ink container (30) includes an opening plug (31) that plugs an insertion opening (30a) where the male connector (41) is to be inserted, and the opening plug (31) includes a reed valve (32) that is pressed by the male connector (41) and opened when the male connector (41) is inserted into the insertion opening (30a), and that is closed by making contact with the male connector (41) when the male connector (41) is pulled out from the insertion opening (30a).