An ultrasonic sensor includes: a first electrode that is provided in an ultrasonic microphone including a vibration element having a function of performing conversion between mechanical vibration and an electrical signal; a second electrode that is provided at a position different from the first electrode in an in-plane direction intersecting a directional axis of the ultrasonic microphone; and a detection section that is provided to detect the presence or absence of attached matter attached to the ultrasonic sensor on the basis of a change in capacitance between the first electrode and the second electrode.