PURPOSE: To obtain a vacuum suction drum possible for sucking an original having two kinds of size or a sensing member by dividing the outer circumference of a drum to two or more regions and providing an independent air chamber to the inside of the drum corresponding to each region.

CONSTITUTION: In sucking a small sized original or sensing member, a valve rod 41 is pushed by a plate spring 50 via a ball 49 and forwarded by controlling the position of the ball 49 at first and the tip part is inserted to a valve seat 42 so as to close the valve. Thus, the air path of an air chamber 28B is closed on its half way. Since the air path of other air chamber 28A is opened normally, only the air chamber 28A is evacuated when a vacuum pump is operated so as to allow the air chamber 28A to suck the original or sensing member 58 to a opened region. In sucking a large sized original or sensing member, a cam 44 is rotated by 90° so as to open the air path connected to the air chamber 28B and both air chambers 28A, 28B are evacuated by the operation of the vacuum pump.