Rotation transmission mechanism and rotary connector

At least one of a plurality of gears includes a tooth-side base portion (10a) and an opposite base portion (10b) that are disposed coaxially and connected to each other by connecting portions (10c), the tooth-side base portion (10a) is formed in the shape of a ring and includes a tooth row (10d) on one peripheral surface thereof, and the opposite base portion (10b) faces a peripheral surface of the tooth-side base portion (10a) opposite to the peripheral surface of the tooth-side base portion (10a) on which the tooth row (10d) is formed. Protruding portions (10e) are formed on the peripheral surface of the tooth-side base portion (10a) facing the opposite base portion (10b). The connecting portions (10c) extend from the protruding portions (10e) toward the peripheral surface of the opposite base portion (10b) facing the tooth-side base portion (10a). A portion, which is connected to the tooth-side base portion (10a), of each connecting portion (10c) and a peripheral surface-tangential direction of the tooth-side base portion (10a) form an acute angle.