A copying machine including an openable original cover, an original holder (11) movably provided on the top of the main body of the copying machine, a locking mechanism (27) provided in the main body of the copying machine and having a projectable lock lever (26) for restricting the movement of the original holder by engaging the receiving parts of the original holder when the original holder is located at a predetermined position, and an ON-OFF detection mechanism (126) for elevating the rock lever a predetermined amount in accordance with the opening and shutting movement of the original cover when the original holder is located at the predetermined postion and actuating a switch (38) for driving the detecting means of the original size.