A scanning apparatus utilizing gravity acceleration for scanning is provided. The scanning apparatus comprises a U-shaped housing, a shaft bearing, a housing and a scanning head. The shaft bearing passes through the housing with two ends thereof respectively and rotationally fastened on two sidewalls of the U-shaped housing, thereby the housing is vertically and rotationally fastened in the U-shaped housing. The scanning head is disposed in the housing with an engageable piece engaged with a hook-type element of the housing so as to fasten the scanning head at a predetermined position close to the top end of the housing. When the scanning head is going to scan, the engagement between the engageable piece and the hook-type element is released and a starting power is applied to the scanning head by gravity acceleration. Thereby the scanning head is guided to move downward to scan via cooperation between a guiding piece and a guiding rail. The scanning speed of the scanning head is determined by the starting power controlled by a predetermined angle contained between the housing and the U-shaped housing.