Provided are a buffer memory operating method used to decompress compressed moving pictures, in which a buffer memory used during decompression of compressed moving picture is efficiently operated to efficiently reduce the capacity of an actually used buffer memory, and a decoding apparatus adapted to the buffer memory operating method. The frame buffer memory operating method includes the operations of decoding a current input I frame and storing the decoded current I frame in a standby buffer and converting the standby buffer having the decoded current I frame into a storage buffer and simultaneously converting a storage buffer having a previous I frame into another standby buffer; and decoding a current input P frame with reference to the decoded current I frame stored in the storage buffer, storing the decoded current P frame in one of the standby buffers, and converting the standby buffer having the current P frame to the other standby buffer.