A patient monitor that acquires and displays first vital sign information and second vital sign information of a subject includes an event detection unit that is configured to detect an activation start event for starting an activation process of biological information processing software which performs a process pertaining to the second vital sign information and an activating event for activating the biological information processing software and a software control unit that causes the biological information processing software to be in a standby state, in which a part of the activation process of the biological information processing software has been performed, when the activation start event is detected by the event detection unit, and causes the biological information processing software to be in an active state from the standby state when the activating event is detected by the event detection unit.
