To provide a method of operating book forming press machine.

In a method of operating book forming press machine, a value relating to a book block 30 is detected on the upstream of the book forming press machine 20 in a direction along a book binding line 10 via a higher-order controller, and this detected value is transmitted to at least a press device and/or a post-forming device and/or a pressing plate for finishing the book block. A means 22 matching at least setting of the post-forming device is called for operation use based on this value detected before finishing of the book block in the direction along this book binding line, determination of the operation position of this means 22 is started for pending processing of each book block 30, and movement of the pressing plate 28 is controlled based on a measured book thickness 34 and the thickness of a cover 18 of the book block in the course of using the post-forming device.