Propeller shaft and yoke structure of universal joint used for the propeller shaft

A propeller shaft comprising:

• a shaft part;
• a first yoke having:
• a fixing portion fixed to the shaft part;
• a pair of first yoke portions having a bifurcated shape that extends from one end portion of the fixing portion in an axial direction, the first yoke portions having four first concave portions, each of the four first concave portions being shaped to accommodate thereon an outer circumferential surface of a fastening tool;
• and
• a pair of first bearing holes, each of the pair of first bearing holes being formed at each of top end portions of the pair of first yoke portions and securing therein a first bearing that holds a cruciform shaft;
• and
• a second yoke coupled to the first yoke through the cruciform shaft and secured to a predetermined member, the second yoke having:
• a mounting flange provided, at a predetermined pitch distance, with four bolt insertion holes, each of which a bolt to secure the second yoke to the predetermined member is inserted to;
• and
• a pair of second yoke portions having a bifurcated shape that extends from the mounting flange toward the first yoke in the axial direction.