A phase change memory apparatus includes: a plurality of sub blocks; a latch block connected in common with the sub blocks through a read bus and configured to latch data from one of the sub blocks; and a comparator connected in common with the sub blocks to receive data from a write bus, and configured to compare data of the latch block with the data of the write bus to generate a comparison signal, which is effective in improving areal efficiency by sharing the latch block among the sub blocks in the unit mat.