A one-bolt type junction box includes a main body in which electrical parts are installed, a lower cover configured to cover a lower portion of the main body, sockets installed on a lower surface of the main body, side connectors installed in the lower cover so as to be coupled to the sockets, a single fixing bolt installed in the main body, a single fixing nut provided in the lower cover so as to be threadedly coupled to the fixing bolt, a central connector mounted in a central portion of the junction box in which the fixing bolt and the fixing nut are disposed, and a connector seating member in which the central connector is seated. The central connector is configured to be mounted on the lower cover in a state in which the central connector is seated on the connector seating member.