Provided is a β-zeolite that has an SiO2/Al2O3 ratio of less than 20 but yet is comparable or superior in heat resistance to conventional β-zeolites having SiO2/Al2O3 ratio of 20 or greater. This β-zeolite is characterized in that: in powder X-ray diffractometry using a CuKα-ray as a ray source, the full width at half maximum of a powder X-ray diffraction peak on the (302) plane is 0.15-0.50 inclusive; and the molar ratio of silica to alumina is less than 20.0. Preferably, the β-zeolite is obtained by a production method which comprises a crystallization step for crystallizing a composition comprising an alumina source, a silica source, an alkali source, a tetraethylammonium cation source and water, characterized in that the composition contains potassium and the molar ratio of potassium to silica exceeds 0.04.