Recently, smart-phones, tablet PCs and so on have been popular and flash memory has been widely used as storage device in mobile devices. It is very important to completely delete files from mobile device for preventing personal information from being disclosed. For this goal, the file wiping technique, which is often used on hard disk, can be applied to flash memory. However, flash memory has the limitation of in-place update differently from hard disk, so deleted data can be extant somewhere on flash memory. Unfortunately, it is possible to recover files which are expected to be deleted. The previous methods of deleted file recovery give rise of unnecessary overhead during recovery or are difficult to apply to flash memory. In this paper, we suggest a new technique for complete file deletion, that is, for preventing deleted file recovery, which is based on a block permutation algorithm used in storing data on flash memory. Through diverse experiments, we show that our method outperforms the existing ones in terms of file recovery prevention.