A sound absorber includes a side surface section (a first wall section) in which a plurality of first holes are provided, the side surface section including a first surface and a second surface, a thin film stuck to the first surface of the side surface section, a partition wall (a second wall section) opposed to the second surface and provided in a position separated from the second surface, at least one second hole being provided in the partition wall, and a porous material provided to be opposed to the second wall section in a position separated from the partition wall.