Rotation position adjustment device and printing system

A rotation position adjustment device (600) includes a first rotation holding section (311), a mark member (350), a sensor (700), and a rotation driving mechanism (500). The mark member (350) includes a mark (M1) provided at a portion of a circumferential direction around a rotation axis (309), and is attached to the first rotation holding section (311) such that the position of the mark (M1) relative to the first rotation holding section (311) in the circumferential direction can be adjusted by an operator, and the mark member (350) rotates integrally with the first rotation holding section (311) when an operator is exerting no external force on the mark member (350). The sensor (700) detects the mark (M1). The rotation driving mechanism (500) adjusts the rotation position of the first rotation holding section (311) on the basis of the position of the mark (M1) in the circumferential direction detected by the sensor (700).