A tubular body of a power transmission shaft made of fiber-reinforced plastic is provided with a cylindrical main body portion, and a second connection portion continuous with an end portion of the main body portion and to which a stab shaft is joined. The main body portion is formed with a weak portion which fails when a load input in the direction of an axial line exceeds a predetermined value. A linear rupture portion is formed on an outer peripheral surface of the weak portion. In the present configuration, cost reduction and weight reduction of the tubular body are made possible, and the tubular body fails infallibly when a predetermined load is input to the tubular body in the direction of the axial line.