A state of a ballast water treatment system of a ship detected by a variety of sensors is monitored by transmitting it to a control means provided with a data storage/transmission means. The control means transmits from a satellite communication means to a satellite communication means on the receiving side via a communication satellite, and a host computer receives it. The host computer analyzes and monitors information from the various sensors S1 to S6 and sends back an optimal operation state, which is received by the satellite communication means on the ship side via the communication satellite, and the control means maintains an operation of the ballast water treatment system based on instructions from the host computer. According to the remote monitoring device for a ballast water treatment system as above, the ballast water treatment system can be monitored and controlled from remote.