In an alkaline battery in which a positive electrode 2 made of manganese dioxide and a negative electrode 3 are contained in a cylindrical battery case 1 having a closed bottom with a separator 4 interposed between the positive and negative electrodes 2 and 3, and an opening 1b of the battery case 1 is sealed via a sealing plate with a gasket 5 interposed between the battery case 1 and the sealing plate, a thickness of a body 1a of the battery case 1 is in a range of 0.10-0.17 mm, and a half-width of a 110 plane of the manganese dioxide measured by powder X-ray diffraction is in a range of 2.30-2.70 degrees.