The present invention provides one kind of scanning instrument including one casing, one transparent platform, one scanning module installed inside the casing for scanning document via shift from some initial position, one drive device to drive the scanning module and make the scanning module return to the initial position after scanning the document, and one control circuit to control the operation of the drive device. After the scanning module stops at the initial position, the drive device is controlled with the control circuit to shift the scanning module to some maintenance position different from the initial position before stopping driving the scanning module to leave from the maintenance position.