A surgical instrument holding device comprising: an adapter from which a surgical instrument is detachable and that is provided with a restricted portion; a separator from which the adapter is detachable; a holding body from which the separator is detachable; and a driving body configured to support the holding body in a rotatable manner and apply a driving force to the holding body, wherein the adapter is provided with a tubular portion through which the surgical instrument penetrates, the separator is provided with an insertion portion into which the tubular portion is inserted, the surgical instrument is held by the holding body via the adapter and the separator, and a restricting portion is formed in the separator, the restricting portion engaging with the restricted portion and restricting rotation of the adapter in a circumferential direction of the tubular portion, wherein a rotation restricted portion is provided in the separator, and a rotation restricting portion is formed in the holding body, the rotation restricting portion engaging with the rotation restricted portion and restricting rotation of the separator in a circumferential direction of the insertion portion, characterized in that a first engagement receiving portion is formed in the holding body, a second engagement receiving portion is formed in the separator, the separator is provided with a first engaging portion that is elastically deformed and engaged with the first engagement receiving portion at a time of attachment of the separator to the holding body, the adapter is provided with a second engaging portion that is elastically deformed and engaged with the second engagement receiving portion at a time of attachment of the adapter to the separator, and the separator is attached to the holding body by engagement of the first engaging portion with the first engagement receiving portion in a state in which the first engaging portion is elastically restored, and the adapter is attached to the separator by engagement of the second engaging portion with the second engagement receiving portion in a state in which the second engaging portion is elastically restored, the rotation restricted portion and the first engaging portion are formed in a shape of protruding with respect to the insertion portion, and the rotation restricted portion and the first engaging portion are provided in such a manner as to be continuous with each other. an adapter from which a surgical instrument is detachable and that is provided with a restricted portion; a separator from which the adapter is detachable; a holding body from which the separator is detachable; and a driving body configured to support the holding body in a rotatable manner and apply a driving force to the holding body, wherein the adapter is provided with a tubular portion through which the surgical instrument penetrates, the separator is provided with an insertion portion into which the tubular portion is inserted, the surgical instrument is held by the holding body via the adapter and the separator, and a restricting portion is formed in the separator, the restricting portion engaging with the restricted portion and restricting rotation of the adapter in a circumferential direction of the tubular portion, wherein a rotation restricted portion is provided in the separator, and a rotation restricting portion is formed in the holding body, the rotation restricting portion engaging with the rotation restricted portion and restricting rotation of the separator in a circumferential direction of the insertion portion, characterized in that a first engagement receiving portion is formed in the holding body, a second engagement receiving portion is formed in the separator, the separator is provided with a first engaging portion that is elastically deformed and engaged with the first engagement receiving portion at a time of attachment of the separator to the holding body, the adapter is provided with a second engaging portion that is elastically deformed and engaged with the second engagement receiving portion at a time of attachment of the adapter to the separator, and the separator is attached to the holding body by engagement of the first engaging portion with the first engagement receiving portion in a state in which the first engaging portion is elastically restored, and the adapter is attached to the separator by engagement of the second engaging portion with the second engagement receiving portion in a state in which the second engaging portion is elastically restored, the rotation restricted portion and the first engaging portion are formed in a shape of protruding with respect to the insertion portion, and the rotation restricted portion and the first engaging portion are provided in such a manner as to be continuous with each other.