According to one embodiment, a memory system includes: a non-volatile memory; a memory interface that reads a received word from the non-volatile memory; a decoder that decodes the received word; a control unit that predicts the number of error bits in the received word read from the non-volatile memory, predicts decoding time on the basis of the number of error bits predicted, and determines an operating clock frequency of the decoder on the basis of the predicted decoding time and requested decoding time being the decoding time requested; and a frequency control unit that supplies the operating clock frequency determined by the control unit to the decoder and supplies voltage corresponding to the operating clock frequency being determined to the decoder.