Disclosed herein are an apparatus and method for sharing memory between computers. The apparatus for sharing memory between computers includes multiple memory adapters, installed in corresponding ones of multiple computers, for receiving an address corresponding to an instruction from the computers and transforming the received address into an instruction in the form of a packet; and shared memory for transforming the instruction in the form of the packet, received from the multiple memory adapters, into an address and performing an operation corresponding to the instruction for a memory cell corresponding to the address.