A power transmission apparatus (10) includes a rotary portion (1) to which turning driving force from a driving source is transmitted and which can rotate, a power cutoff member (3) mechanically connected to the rotary portion (1) and one of the ends of a rotary shaft (5) of a driven apparatus and cutting off transmission of excessive torque between them, and a cap (4) connected to the end of the rotary shaft (5) on one hand and fastened by screw meshing to the power cutoff member (3) on the other hand, and transmitting power from the power cutoff member (3) to the rotary shaft (5). The rotary portion (1), the power cutoff member (3), the cap (4) and the rotary shaft (5) all rotate integrally with one another. The cap (4) has a flange portion (4h) protruding in a radial direction with respect to an axis of the rotary shaft (5) and supporting an axial force.