An air mattress includes a plurality of air cell groups including air cell groups corresponding to the back area, the buttock area and the thigh area of a person lying on the air mattress, each of which groups being made of a plurality of air cells, an air supply/release pump, an air tube connecting the air cell groups corresponding to the back area and the thigh area to the air supply/release pump and connecting the air cell group corresponding to the buttock area to the air supply/release pump in an independent system for each other, and a controller for controlling, when the back area is raised, so that the pressure of the air cell groups corresponding to the back area and thigh area is increased.
