The neuromorphic arithmetic device performs a multiply-accumulate (MAC) calculation using a multiplier and an accumulator. The neuromorphic arithmetic device includes an offset accumulator configured to receive a plurality of offset data measured a plurality of times and accumulate the plurality of offset data, a bit extractor configured to obtain average offset data by extracting at least one first bit from the plurality of accumulated offset data, and a cumulative synapse array configured to accumulate a plurality of multiplication values generated by the multiplier and output a cumulative result of the plurality of multiplication values corrected according to the average offset data.