A turbine bucket is provided that can make centrifugal stress acting on a blade or dovetail not greater than a limit value of a material and that is provided with a shape of a blade root that can ensure a steam passage even if the blade is increased in length in order to increase an exhaust area.The turbine bucket is for a steam turbine low-pressure final stage and has an exhaust area exceeding 9.6 m2 (13.8 m2) in steam-turbine final-stage buckets for a rated speed 3600 rpm (3000 rpm) machine. The turbine bucket is made of martensite steel. A blade portion of the turbine bucket has a suction surface 7 and a pressure surface 8 which are each formed, at a turbine blade root, of three areas consisting of a steam inlet side area 12 with curvature, a steam outlet side area 13 with curvature and an approximately straightly formed area put between the two areas. An airfoil of the turbine bucket root is formed such that the relationship between a blade pitch t and a turbine-axial width BW of the blade portion is BW/t≧5.