The target holding jig which holds a spherical target including a reflection mechanism for reflecting measurement light emitted from a light source, and brings the target and an end surface of an object to be measured into contact with each other, includes a supporting portion configured to support the target being in contact with the object to be measured, a guide portion disposed on a side of the supporting portion facing the object to be measured, regulating a contact position of the target with the object to be measured in a short side direction of the end surface of the object to be measured, and restricting the movement of the target in the short side direction of the end surface of the object to be measured, and a coupling portion fixed to the supporting portion, and removably coupled to the object to be measured.