A method for buffering data in an adaptive streaming service according to an embodiment of the present disclosure comprises the steps of: measuring a per-session throughput and an available bandwidth with respect to traffic generated from a streaming application; determining a number of multiple sessions based on the per-session throughput and the available bandwidth; determining a buffer size for pre-storing data based on a cache hit ratio of the streaming application; and generating at least one request message requesting data based on the number of multiple sessions and the buffer size, and transmitting the at least one request message to a server.