A radio receiving apparatus for receiving variable-length RLC PDU data in an RLC layer is provided that includes a buffer memory sectioned into a plurality of areas having a predetermined maximum data length of the RLC PDU data. By referring to a sequence number SN included in each received RLC PDU data, the radio receiving apparatus stores the RLC PDU data having an identical sequence number SN into an identical area, and assembles an RLC SDU data on a basis of the RLC PDU data stored in each area. According to the present invention, when the RLCU PDU data in the RLC layer is modified to have a variable length, a buffer memory for storing the RLC PDU data received in the radio receiving apparatus can be used efficiently without capacity being wasted.