To provide a diagnostic system of marine equipment using a communication satellite and Internet capable of allowing an equipment manufacturer to rapidly perform the data analysis and other analysis by immediately transmitting the data required by the equipment manufacturer from a ship during navigation.

The diagnostic system comprises equipment 2 for ships, a data logger 3 for accumulating the maintenance data by controlling various kinds of sensors of the equipment for ships, a communication satellite 4 for transmitting the maintenance data transmitted from a ship, a relay station 5 for receiving the data from the communication satellite, and an equipment manufacturer 7 for analyzing the maintenance data received via the Internet network 6 and diagnosing a method of countermeasures of the equipment for ships. When the maintenance by the remote control is determined possible based on the result of diagnosis by the equipment manufacturer, the control data for remote control of the equipment for ships is transmitted to the ships through the Internet network, the relay station, and the communication satellite.