A component of a crank mechanism is incorporated in the crank mechanism that converts reciprocating motion of a piston to rotary motion by means of a crank pin, a crank arm and a crank shaft via a connecting bar, and has a hydrogen content of no more than 0.5 ppm, austenite crystal grains of a grain size number exceeding 10, or a fracture stress value of no less than 2650 MPa. Thus, a support structure in and a component of a crank mechanism ensuring a long fatigue life, high anti-crack strength, and a reduced rate of secular dimensional change to improve dimensional stability, can be obtained.