An air-conditioning system comprising: air conditioning facilities including one or a plurality of indoor units and one or a plurality of outdoor units; a dedicated transmission line that is a network corresponding to a communication protocol dedicated to the air conditioning facilities; a general-purpose equipment controller to which one or a plurality of general-purpose equipment is connected, the general-purpose equipment controller being connected to the air conditioning facilities via the dedicated transmission line; and an energy management gateway, connected to the air conditioning facilities and the general-purpose equipment controller via the dedicated transmission line, and managing the air conditioning facilities, wherein the energy management gateway includes a dedicated communication unit that enables communication with the air conditioning facilities via the dedicated transmission line, a management controller that collects management information preregistered for managing the air conditioning facilities from among various information received via the dedicated communication unit, and a processing controller that controls the air conditioning facilities on the basis of the collected management information, and the general-purpose equipment controller receives or accepts input of running information corresponding to each of the air conditioning facilities and the general-purpose equipment, and controls the air conditioning facilities and the general-purpose equipment on the basis of the running information. air conditioning facilities including one or a plurality of indoor units and one or a plurality of outdoor units; a dedicated transmission line that is a network corresponding to a communication protocol dedicated to the air conditioning facilities; a general-purpose equipment controller to which one or a plurality of general-purpose equipment is connected, the general-purpose equipment controller being connected to the air conditioning facilities via the dedicated transmission line; and an energy management gateway, connected to the air conditioning facilities and the general-purpose equipment controller via the dedicated transmission line, and managing the air conditioning facilities, wherein the energy management gateway includes a dedicated communication unit that enables communication with the air conditioning facilities via the dedicated transmission line, a management controller that collects management information preregistered for managing the air conditioning facilities from among various information received via the dedicated communication unit, and a dedicated transmission line that is a network corresponding to a communication protocol dedicated to the air conditioning facilities; a general-purpose equipment controller to which one or a plurality of general-purpose equipment is connected, the general-purpose equipment controller being connected to the air conditioning facilities via the dedicated transmission line; and an energy management gateway, connected to the air conditioning facilities and the general-purpose equipment controller via the dedicated transmission line, and managing the air conditioning facilities, wherein the energy management gateway includes a dedicated communication unit that enables communication with the air conditioning facilities via the dedicated transmission line, a management controller that collects management information preregistered for managing the air conditioning facilities from among various information received via the dedicated communication unit, and a processing controller that controls the air conditioning facilities on the basis of the collected management information, and the general-purpose equipment controller receives or accepts input of running information corresponding to each of the air conditioning facilities and the general-purpose equipment, and controls the air conditioning facilities and the general-purpose equipment on the basis of the running information.