PURPOSE: To prevent open splice by increasing the bonding area of a tube material by cutting the tube material in a cutting process so as to incline the cutting line in the thickness cross section of the tube material with respect to the longitudinal direction of the tube material.

CONSTITUTION: An unvulcanized rubber material is extruded to form a hollow cylindrical member having a specific thickness and this cylindrical member is cut into a specific length to obtain a tube material and both cut surfaces (a), (b) of the tube material are abutted to produce a tire tube being an endless annular member 10. In the cutting process, the tube material is cut so that the cutting line in the thickness cross section of the tube material is inclined with respect to the longitudinal direction of the tube material. In this case, it is pref. to incline the cutting line so as to cross the longitudinal direction of the tube material at an included angle of below 45°. Since the areas of the bonding surfaces of both cut surfaces (a), (b) can be increased at the time of the mutual bonding of both cut surfaces (a), (b), sufficient bonding strength can be obtained.