A body frame is provided for a riding tractor. An axis of an engine mounted on the body frame is oriented lengthwise along the tractor and a flywheel is provided on the axis of the engine. The body frame comprises a pair of left and right side members extending lengthwise along the tractor, cross members disposed in front and rear of the engine, respectively, so as to connect the left and right side members to each other, and reinforcing members provided on inside portions of the respective side members. The reinforcing members are disposed laterally inward from the lateral outermost end of the flywheel in a space between the engine and each of the side members.