In a processing in memory (PIM) method using a memory device, m*n multiplicand arrangement bits are stored in m*n memory cells by copying and arranging m multiplicand bits of a multiplicand value and m*n multiplier arrangement bits are stored in m*n read-write unit circuits corresponding to the m*n memory cells by copying and arranging n multiplier bits of a multiplier value. The m*n multiplicand arrangement bits stored in the m*n memory cells are selectively read based on the m*n multiplier arrangement bits stored in the m*n read-write unit circuits, and m*n multiplication bits are stored in the m*n read-write unit circuits based on the selectively read m*n multiplicand arrangement bits. A multiplication value of the multiplicand value and the multiplier value is determined based on the m*n multiplication bits stored in the m*n read-write unit circuits.