The present disclosure is to deal with a case in which waterproof clothes, etc. are included in laundry. A washing machine 1 having a dehydration function may include a drum 20 rotatably accommodated in a tub 10, a water-level sensor 60 configured to detect a water level of water IW collected between the tub 10 and the drum 20, a circulation pump 80 configured to supply water to the inside of the drum 20 and to circulate water collected in the inside of the tub 10, and a control apparatus 70 configured to perform a dehydration process. The control apparatus 70 may include a dehydration course decider 74 configured to decide a dehydration course based on a change in water level of water IW collected between the tub 10 and the drum 20 by driving of the circulation pump 80.