A patient monitor (10) acquires a vital sign that is based on a physiological signal of a subject, and an ultrasonic image that is based on a reflected wave of an ultrasonic wave which is irradiated onto the subject. A display section (16) displays information of the subject. A control section (14) switches between a first mode in which a screen containing information of the vital sign is displayed on the display section (16), and a second mode in which a screen containing the ultrasonic image is displayed on the display section (16).