A power transmitting shaft located between a first shaft and a second shaft as a pair of axial members provided between a driving source and driving wheels of a vehicle, the axial members (2, 3) each having an inserting end portion and a fitting groove portion, the power transmitting shaft comprising: a shaft member (4, 5) provided between the first shaft and the second shaft; a joint member provided between the shaft member (4, 5) and the axial member (2, 3) in a direction of a rotation axis of the axial member (2, 3) and having a joint portion (J1, J2) and a tubular portion, wherein the joint portion (J1, J2) is a flexible joint provided at the shaft member (4, 5), and the tubular portion has a tubular portion body, a retaining ring inserting portion (31, 31a, 31b) and a retaining ring fitting portion (32, 32a), wherein the tubular portion body is provided at the joint portion (J1, J2) and has a tubular shape into which the inserting end portion of the axial member (2, 3) can be inserted, the retaining ring inserting portion (31, 31a, 31b) is provided at the tubular portion body and penetrates the tubular portion body in a radial direction crossing the rotation axis of the axial member (2, 3), and the retaining ring fitting portion (32, 32a) is provided at the tubular portion body, opens toward an inner side of the tubular portion body in the radial direction crossing the rotation axis of the axial member (2, 3) and has a shape that extends in a circumferential direction of the rotation axis of the axial member (2, 3); and a retaining ring made of elastic material, characterized in that the retaining ring can be inserted into the tubular portion body from the retaining ring inserting portion (31, 31a, 31b) to fit the retaining ring to an inside of the tubular portion, and the retaining ring fit to the inside of the tubular portion stops a movement of the joint member relative to the axial member (2, 3) in the direction of the rotation axis of the axial member (2, 3) by fitting of the retaining ring into both of the fitting groove portion of the axial member (2, 3) and the retaining ring fitting portion (32, 32a) with the inserting end portion being inserted into the tubular portion. a shaft member (4, 5) provided between the first shaft and the second shaft; a joint member provided between the shaft member (4, 5) and the axial member (2, 3) in a direction of a rotation axis of the axial member (2, 3) and having a joint portion (J1, J2) and a tubular portion, wherein the joint portion (J1, J2) is a flexible joint provided at the shaft member (4, 5), and the tubular portion has a tubular portion body, a retaining ring inserting portion (31, 31a, 31b) and a retaining ring fitting portion (32, 32a), wherein the tubular portion body is provided at the joint portion (J1, J2) and has a tubular shape into which the inserting end portion of the axial member (2, 3) can be inserted, the retaining ring inserting portion (31, 31a, 31b) is provided at the tubular portion body and penetrates the tubular portion body in a radial direction crossing the rotation axis of the axial member (2, 3), and the retaining ring fitting portion (32, 32a) is provided at the tubular portion body, opens toward an inner side of the tubular portion body in the radial direction crossing the rotation axis of the axial member (2, 3) and has a shape that extends in a circumferential direction of the rotation axis of the axial member (2, 3); and a retaining ring made of elastic material, characterized in that the retaining ring can be inserted into the tubular portion body from the retaining ring inserting portion (31, 31a, 31b) to fit the retaining ring to an inside of the tubular portion, and the retaining ring fit to the inside of the tubular portion stops a movement of the joint member relative to the axial member (2, 3) in the direction of the rotation axis of the axial member (2, 3) by fitting of the retaining ring into both of the fitting groove portion of the axial member (2, 3) and the retaining ring fitting portion (32, 32a) with the inserting end portion being inserted into the tubular portion.