To join the front and rear ends of tread rubber correctly without measuring its length and to control the deterioration of precision associated with the length measurement. the extension of process time, the complication of data processing, and the increase in apparatus costs.

A method includes a tread rubber holding process in which tread rubber G is held movably in the length direction, and its rear end Er is grasped by a rear end grasping tool, a press process in which the front end Ef of the tread rubber G is pressed to a molding drum, and a sticking process in which the tread rubber G is moved in the length direction at an adjusting speed so that the rear end Er is positioned to the front end Ef on the molding drum to be stuck, and the tread rubber G is stuck on the molding drum. In the holding process, the front end Ef and the rear end Er are pushed into recessed parts 16, 30 whose shapes are substantially equal with the cross-sectional shapes of the front end Ef and the rear end Er to be held.