An intraoral scanner includes an image sensor, a projection module, a motion sensor, a memory unit and a processor. The motion sensor senses three motion variations corresponding to three axes according to a motion state of the intraoral scanner. The memory unit stores three first variation thresholds corresponding to the three axes. The processor determines whether the three motion variations are smaller than or equal to the three first variation thresholds, respectively. When the processor determines that at least one of the three motion variations is smaller than or equal to the three first variation thresholds, the processor enables the image sensor and the projection module. When the processor determines that all of the three motion variations are larger than the three first variation thresholds, the processor disables at least one of the image sensor and the projection module.