An overhead scanner includes a main body, a rotation unit supported by the main body and being rotatable around a rotation axis, an imaging unit mounted on the rotation unit and is configured to read a medium placed on a placement surface below the rotation unit, a light source that irradiates the medium with light, a driving unit that moves the rotation unit around the rotation axis toward a placement side, where the medium is placed, and a posture change detecting unit that detects posture change of the main body. When it is determined that the main body falls down based on the posture change detected, while the rotation unit is located at a readable position for reading the medium, the driving unit moves the rotation unit toward the standby position where the rotation unit is located when the imaging unit does not read the medium.