Disclosed is a detergent supply device having an improved locking structure and a washing machine including the same. The washing machine includes a main body, a tub disposed inside the main body to accommodate water, a detergent case configured to supply a detergent to the tub, and a locking device configured to detachably connect the detergent case to the main body, wherein the locking device includes a first locking member disposed in the main body, and a second locking member disposed in the detergent case to unlock or lock the first locking member by being pressed or released.