PREHEAT oven to 375° F. Grease 13 x 9-inch baking dish.
MELT butter in large saucepan over medium heat. Add celery and onion; cook, stirring occasionally, for 1 to 2 minutes or until vegetables are tender. Stir in noodles, tuna, soup and evaporated milk; mix well. Pour into prepared casserole dish. Sprinkle with potato chips.
BAKE for 25 to 30 minutes or until chips are golden brown.