An infusion set includes a first infusion line set that forms a first infusion line with an injection port; and a connector including a male connector end that is insertable into the injection port, a female connector end to which a second infusion line can be connected, a flow channel, and a partition. The injection port and the connector are configured such that, when the male connector end of the connector is inserted into the injection port, the flow channel of the connector is divided by the partition into an in-flow channel configured to let in a liquid from the injection port in the first infusion line and an out-flow channel configured to let out the liquid that has entered the in-flow channel to the injection port.