A door locking device which is reduced in size relative to a conventional device includes a key operation transmission link, which transmits a key operation force relative to a key cylinder to a relay lever corresponding to “a lock switch member”, and which is arranged to rotate about a common rotation axis shared with the relay lever. In addition, a rotation space for first and second movable contact portions fits within a circular-shaped area around the common rotation axis because a first fan-shaped protruding portion including the first movable contact portion for transmitting a force to the key operation transmission link and the relay lever and a second fan-shaped protruding portion including the second movable contact portion for transmitting the force to the key operation transmission link and the relay lever are arranged around the common rotation axis.