Air mattress for gatch bed

An air mattress for a bed, placed on a plurality of bottoms including a back bottom and used for the bed that performs a back raising operation for raising the back bottom, comprising:

• a plurality of first air cells extending to a first direction and being arranged in parallel in a second direction, the first direction being different from the second direction;
• two second air cells extending to the second direction, the first air cells being disposed between the two air cells;
• a first unit capable of inflating and deflating each of the first air cells;
• and,
• a controller configured to control to alternately inflate and deflate the air cells by successively increasing and decreasing a pressure of air to be supplied to each of the first air cells, wherein:
• the first unit inflates and deflates the first air cells by n lines independent from each other, where n is a natural number equal to or greater than 3, and
• the controller performs controlling of inflation and deflation of first air cells of one line during at least a part of a period in which a back bottom is being raised.