SECONDARY BATTERY

A secondary battery includes an electrode assembly, a case accommodating the electrode assembly, and a cap assembly coupled to the case to seal the case, and the case includes a bottom portion, long side portions bent and extended from the bottom portion, a first short side portion bent and extended from the bottom portion, and second short side portions bent and extended from the long side portions, the first short side portion and the second short side portions connected to each other to define a short side portion, and curvatures located between the first short side portion and the second short side portions.