To provide an ultrasonic wave propagation speed measuring apparatus that can take measurements in a short time and be incorporated into a fiber manufacturing line while reducing measuring errors, being applicable also to a fiber bundle consisting of numerous fibers, and providing for completely nondestructive assessment that causes no irreversible changes to articles to be measured; and a carbon fiber manufacturing apparatus having the measuring apparatus.

The ultrasonic wave propagation speed measuring apparatus 10 includes an ultrasonic wave generation means 13 for generating ultrasonic waves inside a fiber bundle; a first and a second ultrasonic wave detection means 14, 15 disposed in two different positions away from the generation means 13 in the same direction for detecting the ultrasonic waves propagating within the fiber bundle; a detection time measuring means 18 for measuring the time that the detection means 14, 15 take to detect the waves; and a processing device 19 having a drive control part for the above means and a computing part for the propagation speed of the ultrasonic waves. The fiber bundle within which the propagation speed of the ultrasonic waves is to be measured is moved/stopped by nip rollers 11, 12 and given predetermined tension. The ultrasonic wave generation means 13 and the ultrasonic wave detection means 14, 15 are pressed against the fiber bundle by a pressure contact means 17.