A probe assembly includes: a measurement probe having a plurality of optical fibers configured to propagate light, emit the light to a measurement target, and receive scattered light returned from the measurement target and an end cover having: an endoscope holding portion configured to hold an insertion portion of an endoscope, the insertion portion being configured to be inserted into a body cavity of a subject and a probe position defining portion configured to define a position of a distal end surface of the plurality of optical fibers of the measurement probe.
