An apparatus and method for processing data in a Massively Parallel Process Array (MPPA) system are provided, in which a scheduling processor determines an array processor and an initial memory, and requests halt release to the array processor, which requests allocation of an additional memory or return of used memory to an address conversion controller, if allocation of additional memory or return of used memory is needed during program execution. The address conversion controller controls, upon receipt of the request for allocation of additional memory, conversion of a base address of additional memory to a physical address and, upon receipt of the request for return of used memory, deletes registered information from the address conversion table. The array processor requests return of additional memory to the address conversion table and transmits a terminal signal to the scheduling controller, upon completion of the program.