To provide a tire air pressure alarm device capable of giving an alarm including a user's intention.

When a tire air pressure is determined to be out of a target air pressure range on alarm factor items, such as fuel saving, prevention and safety, comfortableness, and flat tire, selected by a user, an alarm is given to the user on the alarm factor items selected by the user. Thus, on only the alarm factor items selected by the user out of a plurality of types of alarm factor items, the alarm is given to the user, thereby giving an alarm reflecting the user's intention.