A battery (2) comprising a pressure sensitive adhesive sheet (1) and an electrolyte solution, wherein: the pressure sensitive adhesive sheet is provided at a site in the battery in which there is a possibility of contact with the electrolyte solution; the pressure sensitive adhesive sheet comprises a base material (11) and a pressure sensitive adhesive layer (13) laminated at one side of the base material; and the pressure sensitive adhesive layer (13) is formed of a pressure sensitive adhesive composition comprising: a (meth)acrylic ester polymer having a main chain containing (meth)acrylic alkyl ester monomer units having a carbon number of an alkyl group of 6 or more and 20 or less, and carboxy group-containing monomer units, wherein the (meth)acrylic alkyl ester monomer units having a carbon number of an alkyl group of 6 or more and 20 or less contain 2-ethylhexyl (meth)acrylates and (meth)acrylic alkyl ester monomer units having a carbon number of an alkyl group of 10 or more and 20 or less.