This invention relates to a lithium secondary battery, the tab shape of which is improved, thus increasing the safety and improving the electrical properties thereof. The lithium secondary battery includes an electrode group composed of a first electrode, a second electrode, and a separator disposed between the first electrode and the second electrode, a first electrode tab connected to the first electrode, and a second electrode tab connected to the second electrode. The first electrode tab includes a first portion connected to the first electrode and a second portion, which is not the first portion, the width of the first portion being less than the width of the second portion.