The present invention relates to a device for providing a quality of service (QoS) of a hand-off between heterogeneous networks, and a method thereof. According to the present invention, the device includes a device for performing a QoS management function for each access system and a device for performing a QoS management function between heterogeneous access systems in a network including a plurality of interlocked access systems. The device for performing the QoS management function for each access system manages a user service session, a local QoS of the access system, and a QoS context of the service session. The device for performing the QoS management function between the heterogeneous access systems negotiates the QoS of the service session and manages the QoS context when the hand-off is performed between the heterogeneous access systems, and performs a QoS mapping operation.