An adaptor for detachably connecting a surgical instrument to a robot arm of a robotic surgical system according to an embodiment may include: a base body including a first surface to be attached to the robot arm and a second surface to which an attachment surface of the surgical instrument is mounted； and drive transmission members rotatably provided on the base body. The second surface of the base body includes first and second guide rails respectively corresponding to first and second guide grooves provided on the attachment surface of the surgical instrument. The first and second guide rails of the second surface are configured to be inserted respectively into the first and second guide grooves of the attachment surface, and guide the surgical instrument to be slid to a position where the drive transmission members respectively correspond to rotation members provided on the attachment surface of the surgical instrument.
