A toothed belt power-transmission apparatus includes: a toothed belt which includes a cord and a plurality of belt tooth portions; and a plurality of toothed pulleys which include a plurality of pulley tooth portions. The cord includes a carbon fiber cord formed by combining and secondarily twisting a plurality of primary twisted yarns including a carbon fiber. A twisting direction of a primary twist of the primary twisted yarns is the same as a twisting direction of the secondary twist. A primary twisting coefficient of the primary twist is 0.62 to 1.30. A secondary twisting coefficient of the secondary twist is 2.06 to 3.95. A tooth pitch of the toothed belt is within a range of −0.4% to +0.1% relative to a tooth pitch of the toothed pulley around which the toothed belt is wound.