Abstract: Provided are an apparatus and method for writing data to a phase-change random access memory (PRAM) by using writing power calculation and data inversion functions, and more particularly, an apparatus and method for writing data which can minimize power consumption by calculating the power consumed while input original data or inverted data is written to a PRAM and storing the data consuming less power. A PRAM consumes a significant amount of power in order to store data in a memory cell since a large electric current is required to flow for a long period of time.