This paper describes a simple reusable device that hydrodynamically traps a large number of beads in an array. The device allows us to release the trapped beads by simply reversing a flow direction. The trap and reset operations are extremely simple, robust and highly efficient. With the device, we succeeded in arraying 1000 microbeads, and subsequently releasing them in a few minutes. As the demonstration of the resettability of the device, we performed two sequential assays and found that multiple experiments can be easily conducted, saving both cost and time.