A key unit authenticates a portable terminal based on information acquired from the portable terminal and controls locking and unlocking of a target by transmitting a signal to a locking and unlocking device. The key unit includes: a first communication unit configured to receive a request signal transmitted in a first frequency band from the locking and unlocking device; a controller configured to authenticate the portable terminal and process signals transmitted to and received from the locking and unlocking device; a second communication unit configured to perform short-range wireless communication with the portable terminal in a second frequency band; and a substrate on which the first communication unit, the controller, and the second communication unit are mounted. The first communication unit and the second communication unit are mounted at positions facing each other across the controller, on the substrate.