PROBLEM TO BE SOLVED: To provide a mattress apparatus capable of changing the support part of a users body by a fluid bag without shaking the users body.SOLUTION: A mattress apparatus includes a plurality of fluid bags 2 longitudinally juxtaposed in two vertical stages on the upper face of a base member of rectangular plate shape so that the longitudinal direction is extended along the width direction of the base member. The fluid bags 2 are divided into two groups on the whole by forming one group of the plurality of fluid bags located in mutually non-adjacent positions in the upper and lower stages. The plurality of fluid bags in one group and the plurality of fluid bags in the other group are connected such that a fluid from an air pump 3 is supplied through a switching means 4. A control device 15 switchingly controls the switching means 4 such that the fluid is alternately supplied to the plurality of fluid bags in one group and the plurality of fluid bags in the other group.
