According to an embodiment, an authority changing device includes a first determiner, a second determiner, and a changing unit. A first authority is defined by a first combination of first to third item values, and a second authority is defined by a second combination of the fourth to sixth item values. The first determiner uses a logical expression to determine whether the change from the first authority to the second authority is possible, not possible, or unknown. The second determiner uses a first table to determine the availability of change from the first authority to the second authority when the availability of the change is determined to be unknown. The changing unit changes the first authority to the second authority when the change is determined to be possible.