A spin cycle controlling apparatus for a washing machine includes a storage unit in which an acceleration rate, an allowable maximum unbalance amount and an allowable minimum unbalance amount according to an amount of laundry are pre-stored; and a controlling unit for repeatedly controlling an operation of increasing and decreasing revolutions per minute (RPM) in a region between the allowable maximum unbalance amount and the allowable minimum unbalance amount until an unbalance amount detected is less than the allowable minimum unbalance amount.