A QoS degradation point estimation device includes a flow set decision unit, a flow quality information collection unit, a path information collection unit, a flow link table management unit, and a QoS degradation point estimation unit. Before generating a flow link table associating QoS of a flow through a network with a link the flow passes through, the flow set decision unit preferentially selects a flow passing through almost ½ of the links of the network as a flow to be registered in the table. The flow quality information collection unit collects information of the QoS of the flow. The path information collection unit collects path information of the network. The flow link table management unit generates the table based on the information of the QoS and the path information. The QoS degradation point estimation unit estimates a QoS degradation link based on the table.