PURPOSE: To enable accumulated printed pages to be furnished with high speed into a bundler by transferring the accumulated printed pages for a predetermined number of printed books delivered from a folding machine and clamped forward and backward in the pushing direction of a pusher into the bundler for bundling said accumulated printed pages.

CONSTITUTION: A bundler 19 for a printed book stacker has a stacker 20 provided with a fork 22 for accumulating printed books 5 transferred by a conveyer 80 in a hopper 60 to drop down every lot and a turntable 24 disposed below the fork to regularly reversely turn by every 180° for receiving each lot and accumulating the printed books. Also, the bundler 19 has a pusher 43 for delivering sidewise the accumulated printed books in the stacker 20 and a bundler 50 for binding this accumulated printed books. The bundler 50 is provided with a slide member 53 fitted in a groove 52 formed on the upper surface of a conveyer table 51 and extending in the direction of conveying the accumulated printed books and a front holder plate 54 urged normally leftward through a wire 56 by a weight 57 by said member 53 to cooperate with a pusher plate 44 of a pusher 43.