PROBLEM TO BE SOLVED: To provide a document management device capable of automatically eliminating a file attached to work flow tentatively kept in a client terminal during work flow processing at appropriate timing, a method of controlling the device, a document management system and a method of controlling the system, and a program.SOLUTION: A CPU 201 of an approver terminal 300 receives approval flow from a server 400 and refers to or obtains a file of an approval object. When the file of the approval object is referred to, the file is automatically eliminated. When the file is preserved, an approver is urged to decide whether or not to eliminate the file, and the file is eliminated when elimination is instructed.