A Data Over Cable Service Interface Specifications (DOCSIS) frame reassembling apparatus and method in a cable modem including a plurality of receiving channels is provided. A method of controlling reassembling of a Media Access Control (MAC) frame, the method including: receiving a signal and outputting a packet signal through demodulation and error correction; receiving the outputted signal and controlling a specific compression format standard header and a point field; receiving packet data and a buffer write enable signal, and writing data in a MAC frame reassembling buffer; storing the data written in the MAC frame reassembling buffer; and reading the stored data from the MAC frame reassembling buffer in response to a received buffer read enable signal, and storing the read data in a MAC frame buffer.