a storage memory configured to store N-bit read data and N reliability data units each indicating reliability information for a corresponding bit of the read data;

a decoder configured to execute a decoding operation for the read data based on the reliability data units; and

a processing circuit configured to:

read first read data from a memory area located outside the controller based on a first read bias,

read second read data from the memory area based on a second read bias,

calculate a first syndrome weight corresponding to a number of syndrome elements having a preset value in a first syndrome of the first read data,

calculate a second syndrome weight corresponding to a number of syndrome elements having a preset value in a second syndrome of the second read data,

determine, as the read data, one of the first read data and the second read data based on which of the first syndrome weight and the second syndrome weight is smaller, and

determine a value of a reliability data unit corresponding to I-th bit of the read data based on an I-th bit of the first read data, an I-th bit of the second read data and a difference between the first syndrome weight and the second syndrome weight.