PURPOSE: To avoid the breakage and cutting of a tooth due to the separation of a seamed portion of a canvas as a surface member, and improve the durability of a belt, by inclining a direction of a seam line of the seamed portion at a predetermined angle relative to a tooth trace and locating a part of the seam line on a tooth flank other than a bottom land and a root of tooth.

CONSTITUTION: A canvas 3 to be bonded by curing to a rubber 5 and formed into a tooth profile of cylindrical internal teeth is seamed cylindrically. A seam line is inclined at a predetermined angle θ relative to a direction of a tooth trace in such a manner that the angle θ is not less than a critical angle θ0 defined according to a width (FE) of a belt 1 and a width (FH) of a bottom land B and that a part of the seam line is located on a crest A of the tooth profile. Accordingly, the seamed portion intersects a root C of tooth at one point, thereby reducing the influence of a repeated stress. Even if a thread of the seam line at the root C and the bottom land B is partially cut by the influence of the repeated stress, the seam line at the crest A of the tooth profile is not damaged to prevent the seamed portion of the belt from being entirely separated. Thus, the belt is prevented from being cut during operation, and normal operation can be continued owing to the superior durability.