Work support system and method with screen sharing and development system for multi-platform application disclosed. The work support system with screen sharing includes a customer terminal in which a service application is installed and executed, an employee terminal configured of sharing and displaying a designated area of an execution screen of the service application, and a work support server configured of communicating with the customer terminal and the employee terminal, and supporting a customer work by setting a screen of the customer terminal to be shared in the employee terminal under a specified condition.